I can't do much more to educate you than repeat what I just said. They don't "believe" it exists. It is an hypothesis based on models that have been shown to have predictive value. Now they are trying to confirm that hypothesis. If the hypothesis is confirmed great. If not new hypothesis will come. There is no faith here. If there were faith they wouldn't bother looking for it and try to look for data to confirm or disprove their models. They'd just assume it to be true.

Actually it is exactly the other way around. The fact that they spend billions to confirm its hypothesised existence, rather than just take it for granted, is a consequence of their lack of faith.

Still, the way you put it, doesn't sound like a technological or engineering challenge, but mere budget. So I have to wonder how much costs would have to increase to get there in 1/4 of the time.

You already got a really nice response here, but let me just add a few things.

If you like the "multiple desktop" metaphor then think of activities as different "offices", these are different works spaces that you can go to to perform different tasks, and each office may have it's own decorations, all different kinds of appliances on sight, some appliances always running by default, and possibly multiple desks to put your stuff. Unfortunately the implementation is still (in my opinion) a bit primitive. But eventually it should provide you with all different kinds of office spaces (activities) optimised to work in a certain kind of way, and furthermore make it easy to define your own.

For instance, you could have your Programming Environment. Here programming tools as icons on desktop and panel. By default it could open a couple of konsoles with different tabs in common directories in one of the virtual desktops. In another maybe Git client logged in to your main repository and another konsole. Of course you could be running two such activities of this same kind, one for your Java project and another for some Haskell project, and alternate between both. And when you're not using one of them you could pause it, and ideally in practise this could work as a local "suspend" or "hibernate", i.e. free your processor and possibly memory until you want to return to it and have everything back up running again in the previous state.

The confusion arises because there's a small paradigm change. You now have activities, which are more generic. The idea is that you run an activity for each particular task you want to accomplish, therefore each activity may have completely different settings and even provide you with completely different user interfaces. And in that context a virtual desktop becomes just a bit of extra space within an activity.

Now you may still say want a wallpaper per desktop anyway, but that's not any more sensible than asking for say, different icons per desktop. And of course this can be generalised to any particular widget. So KDE provides you with an option to change those widgets per virtual desktop. You looking for a specific option for wallpaper only, is a result of your habits based on the fact that previously, there wasn't much else you could change.

If you want to share the same things in the same way with all of your acquaintances, by all means do it. But that's not how most people behave. To me, circles brings me back to the real world.

Facebook worked fine when it was mostly Uni students. This meant the contact list was somewhat uniform. But while in the beginning most shared pretty much anything over Facebook, I see more and more people now protecting their tagged photos, removing albums, disabling walls. They don't feel that comfortable sharing all that stuff with their aunts, their boyfriend's mother, boss. So they are using Facebook less and less. I have 15 year old cousins who have 0 interest in getting a Facebook account.

If you want to share things with just your close family members, or just close friends, or just computer scientists... how do you do it? You create the respective lists. Initial problems.
- They will see the names of the groups and how you organized them (not good for "not so close friends", "hot girls" and the like).
- How do you find which pictures you've share with just a particular group of people?

But you also want to talk back and forth with them, wall style. You can restrict your wall to just certain lists, but you only have one wall... so you need a group for each list. Problems:
- They will see the name of the groups.
- Now you want to start a particular discussion with two lists, or with one list plus one person... create new group just for that?
- You have to go to your groups to look at your discussions with that particular groups, no overall view of your discriminated stream.

It is way to messy. Circles on the other hand, are not an afterthought. All your contacts are organized in circles, you share whatever you want with a particular circle, or any group of people you define on the fly. I still think the interface needs to improve a lot, and as well as the basic concept (we need at least sub-circles). But still, even as it is, it's already way better in terms of control of information.

From the linked announcement, which you obviously didn't bother to read:

That's part of the point of "activities". KDE should provide you different interfaces for different tasks. If you go to the cashew and select "activities" you have a few activity templates available, such as the "search & launch". So far nothing very interesting is available, but to be fair from what I understand the internals only recently became usable, so I'd expect the situation to slowly change.

This is not the case, you probably missed the slashdot story on the drama between GNOME and Canonical. In particular see Aaron Seigo's rant on how GNOME ignored "status notifiers", a cross desktop specification submitted to Freedesktop.org and with an existing implementation by Canonical.

GNOME's latest release is actually 2.32. Version 3 wasn't released yet.

My guess is couples using condoms feel much more comfortable not withdrawing than couples using the pill (that's my experience anyway). So it might be the case that, unless they had specific instructions not to withdraw, many of the couples using the pill often used both these methods combined.

Konqueror did it before Safari.

F6 selects the text in the URL bar. In practise this is more general than clearing. You can simply start typing and the previous text will be gone (and if you don't want to type new text you don't have any reason to clear it). On the other hand you can also for instance, simply copy the text, or move your cursor and edit it.