That Gnome 3 complaint is almost certainly a for-technical-reasons one. The problem is that you can look at a window and observe that it's open, and make a good guess about which app it belongs to, but that doesn't necessarily give you enough information to be able to open another copy of the app.
(I've been looking into the technical details behind this in an attempt to improve it for Unity, and I'm reasonably sure there's no 100% reliable way to figure it out. Unity's solution seems to be just to randomly fail when it can't figure it. Gnome 3 is presumably only making it possible when it's sure it'll work.)
I tried using the Ribbon for a while. I found that it was mostly intuitive (although try finding something like the double underline in Microsoft Word if you don't already know where it is; it's awkward in both pre-Ribbon and Ribbon versions, but somewhat harder with the Ribbon), but my main issue is simply that it takes more clicks. With toolbar+menu, if something's used a lot it's on the toolbar in a known place and can be accessed with one click. If something isn't used a lot, I can still access it through the menus. On the other hand, with the Ribbon, the number of clicks it takes to do something depends on whatever you did last, so it's not only more for common tasks than a menu+toolbar is on average, but it's also inconsistent; unless you do a useless click on a Ribbon tab even if it's already open, your muscle memory is going to be screwed up.
(And another observation: why isn't the "save" button on the ribbon in Microsoft Office programs? It got moved to a separate area precisely because it's commonly used and the Ribbon is bad at handling commonly used commands.)
I have spam filters, but they're set not to delete spam mail I receive; rather, they just tag it as spam in the subject line and let me choose whether or not to read the mail. So I guess I check the caught spam every time I check my email.
On the other hand, I don' t think I ever check for messages deleted by my Usenet killfile. Spam is one thing, but trolls are another.
The miners put most of the computational effort in for you; typically you pay a small fee to encourage them to put your transaction into the chain. Usually the buyer will pay the transaction fee, and the seller won't count the sale as complete until it goes sufficiently far back in the train. (In other words, while Bitcoin transactions are instant, it takes a nontrivial amount of time to determine for a fact whether a transaction happened or not. And as such, a cautious seller won't release the goods immediately, but wait until there's enough effort in recording that version of events that nobody's unlikely to override it with a new one.)
So if the mining stopped, nobody would be recording transactions any more. As such, double-spending would be trivial; you could repeatedly do a small amount of mining to satisfy one person that they had the coin, then a bit more to change the history's idea of where the coin went and give it to someone else (or a second account you control). As such, people would have to wait for a very long time in order to be satisfied that a transaction were genuine if there were no mining, and this would make transactions basically impossible. A currency is worth nothing if you can't meaningfully trade it.
It's a proof-of-work calculation that records a transaction history. Basically, it's to prevent double-spending; if someone attempts to transfer the same bitcoin to two different people, the person who gets it is the person who had more computational effort go into recording them as having it. If the amount of computational effort in recording transaction histories were low enough, someone could double-spend by recording an alternative history on a powerful computer and having it supersede the transaction history everyone thought they were using.
In order to encourage people to put effort into recording the history, there's a reward for doing so. This lead (perhaps predictably) to "mining", where people race to record the transaction history first in order to get the reward.
So there is a purpose to mining, but it's only to keep the Bitcoin system itself running. If people stopped mining (perhaps because the reward got low enough), Bitcoin would collapse. (It's envisaged that once the mining reward gets low enough, people transferring bitcoins will pay a transfer fee to the miners to encourage them to keep mining, and they'd get their income that way instead.)
Reading the ruling (it's at the last link in the summary) is quite interesting. Basically what happened is that Apple tried to exploit technicalities in the judge's wording, and the judges found a bunch of technicalities in Apple's statement to find it invalid anyway.
(For instance, the judges focused on the facts that the court case had nothing, technically, to do with the iPad, and that patents weren't involved, both of which contradict Apple's original statement.)
Systems programmers are the high priests of a low cult. -- R.S. Barton