I estimate that 10% of the users will go to other sources for information, because this type of ads are really frustrating. If I war an advertiser this is one type of ad that I will not want in my ad campaign, the users try to skip it as soon as possible, so in return I don't really get the result I would like to (conversion).
I could put up with the amounts of ads on the website but this is just getting silly now, and to make matters worse, the link they tweeted went to a 404 page (it happens sometimes for me and I guess its something to do with the CDN not caching for europe quick enough)
I believe it only shows up once. I've seen it the first time I went to TechCrunch today and now it isn't displaying anymore.
Also, it appears to show only while the page is loading.