1 I haven't seen it either, but I took it off Ace's site after people complained, and it does seem to have been the cause of the problem.

2 I was being redirected very rarely - maybe once a month.  I can't be certain it was anything on your site (I've heard rumors that some ISPs inject ads now), but I'll let you know if it happens again now that Sitemeter is gone.

3 I was getting redirected from here and neoneocon.com on a regular basis, and went as far as to change my antivirus programs twice thinking it was malware that was somehow slipping past them.
It's good to know what the real source of the redirect was, but it's sad how any trusted software seems to be up for sale to ad spammers these days.

4 I was never redirected, but I also have adblock+ running and it was catching Sitemeter cleanly. 

5

They say, "If you're not paying then you aren't the customer, you're the product." That's certainly true for lots of web sites and web services.

Sitemeter has a paid version with more features but I suspect it isn't very commonly used and likely they decided they needed some more revenue. Random redirection to ad sites, however, is a shortsighted approach to monetizing their product. In the short run it probably did cause a stairstep in revenue, but it also damages the brand and will lead to a long term decline in usage.

6 I suspect a lot of companies have decided that random redirects are a good way of monetizing eyes. Being random, it's more difficult for the annoyed web surfer to assign the blame.
Why advertisers are so keen on getting views by pissed off people, I'm not so sure. Must be that they're so cheap per eyeball-second that even pissed off viewers are worth it.

7 Recently Pajama media and Powerline started using something that causes pop-behinds. I've got the site that gets linked to blocked, so I get the extra window but with nothing in it, but I can't figure out what JS include file is doing the dirty deed. And it isn't easy to trace down because it only happens once per day per site. (It isn't from the site I've blocked.)

8 With sitemeter, even if you were a customer, you were still the product. Ann Althouse was a subscriber, and had issues. 

9

Powerline, Breitbart, Hot Air, and This Ain't Hell all have problems with redirects, as well as malware in the ads themselves at one time or another.  That is why I have become rather wary of visiting them, as well as TV Tropes and Sankaku, even after I put ad blocks and anti-exploit software on my system (I am positive the former had malware in their ads which require much effort to clean up.).

Even National Review Online has the redirect problem, which is quite annoying.

Even Ace of Spades HQ had problems with malware in the ads they were running for a while, enough that my security software was raising red flags during several visits to Ace of Spades.