To distress my enemies, I'd force on them ...

In some cases I can deal with interstitials, but not on mobile browsers. I suppose the content hoster got their ad-view, but half the time they malfunction to the point of completely breaking the page content, or not being dismissible!

My ex-wife.

this question was sponsored by an online ad agency to see which type of ad has the best mindshare ROI...

Ads that play sound

Ads that interpret a "close" action as "user clicked on the ad".

This seems to happen with ads that hover over the content and require that one click a "close" box (either with the word "close" or with an "X" -- this isn't a pop-up with the standard browser close-window icon).

ad block and filters can't work if the ads really are hosted on the same IP as the content. I'm suprised no large advertiser has made this the new model. Example: advertiser hosts slashdot.org, and the advertiser's proxies pull in slashdot's content via authenticated channel we the users can't reach.

so it sits there hiding in a browser tab you've long since forgotten then starts making porno like sounds

Which form of advertising will offend its user base the least when they finally remove that little check box?

Google (along with the NSA, CIA, FBI, Chinese Government and a hoard of others) all know everything I do. Why are the ads I see so badly targeted? I spend lots of money online and in the real world, and I can't remember the last time saw an ad for something I actually wanted. When ads are targeted they are always late - ads for hotels in cities I've just left, ads for new computers or cars just after I've bought one.

The popover ad that cannot be closed on a mobile device because the Close button is stuck off screen.

Any ad that isn't clear about what it's advertising nor confined to a well-defined space on a static page.

...beats a blipvert.

No, product placements. At first you think, "how could that be as annoying as a moving ad?", which was the option I picked. Then you start thinking of how product placement blurs the boundaries. A well-crafted placement lures you into thinking you're just watching a show. You have to be consciously looking for them. You question your values. Wait... Wrigley Stadium. It's an institution. Why can't the new named stadiums be like that? The would-be questioner of consumerism gets lost in a morass, loses his moral compass, and ends up blathering on about it in a post like this one, which is brought to you by Wrigeley's Spearmint.

I would force on my enemies the Slashdot Beta over interstitial ads.

(as a side note, just checked out the Beta.... wtf? no improvements after 4 months now?)

So I go to a web site to download a nifty-looking piece of software, and right there in the middle of the download page there's a big "Download" button. Except it's really an ad for a totally different piece of software. Whose bright idea was it to hide the product they've already sold me on?

But if I did, the ads that play sound would be the ones I'd throw at my enemies.

Do people really have enemies? I mean real people, not people in TV shows, politicians or religious nutheads. There's a few people I dislike, I guess... my solution to that is to avoid their company. Problem solved.
Who really dislikes someone so much that they'd actually spend time making them miserable?

Knead I say moore?

For awhile I had that "in thanks for your contributions, you can disable ads" checkbox available. I didn't really care since the ads were inobtrusive and I figured supporting the site was a good thing. Then Beta happened, and while that was annoying, I still didn't care about the ads.

But maybe a month ago, /. started having those overlay ads on the bottom of the browser frame. It was time to tick the checkbox. Everything was fine for maybe a week... then bam, ads again.

Short story is, I installed NoScript.

I'm a bit torn, because it's the details that can make things really annoying. For example, an interstitial ad with a clear link that says something like "Click here to skip" isn't so bad. An interstitial ad that makes you watch a >=30 second video before continuing is really annoying. And if we're wishing this on our enemies, are we talking one every so often (not so bad) or one on every web page they visit (in which case it would be the worst)?

For ads that pretend to be security alerts, how technically competent is our enemy? If it's clear to them that it's an ad, then it's just like any other ad. But if our enemy is not a technical person and they don't know it's an ad, and see it so often they assume something must be wrong and proceed to enter in their credit card number to "fix" their security issue and install malware, then this would be the worst.

Do the pop-under ads have sound? Pop-under ads can be easy to ignore, but if they have sound then they are a major nuisance. If they have Flash then stack a few dozen of them and they can seriously slow things down. Is there a loud annoying Flash pop-under for every page they visit? This could be the worst then.

...ads that somehow manage to evade both ScriptSafe and AdBlock Plus.

Personally, if I was going to inflict ads on my enemies (as opposed to, for example, repeatedly stabbing their genitalia with a fork until they fall off), I would probably go for pop-over (always on-top, of course) ads that claim to be either security alerts or flashing advice that they have won something, and all they have to do to claim their $1 million is click on the ad, which then move when you try to click on them.

Not that they would affect me.
now if you will excuse me, I need to go get some lightspeed briefs.

Ads that look like a download button. They have been getting better on that, locating it near the content and not having any other text around it except maybe a tiny (outside offer) or something similar nearby, if you are lucky.

It used to be that it was only pretty shady websites you'd see this on, but more and more I'm seeing this on supposedly reputable sites. Even Sorceforge. It's a massive loss of reputability in my mind.

Almost anything else can be made acceptable through some combination of good design, but if I ever hear even the tiniest peep from an ad your site gets adblocked until the end of time.

Lots of kittens.