Yep, adblock. I think websites like youtube deserve ad revenue, but when the ads reach a certain level of obnoxiousness, they drive consumers to find ways around them. Adblock is just one example. Some others:
DVR's allow you to record shows and fast forward through advertisements. Similar technology could have been around years prior, but only in recent years have television advertisers begun to increase the volume of their ads by 50% and increase the ratio of show to ads all the way up to 1:1. (Meaning, you spend just as much time watching ads as you do watching the show. The Lost series finale was like this, I think the entire episode was only 30 minutes long.) Now DVR's, Netflix, Hulu, and other mediums have become a very serious industry, and it isn't just because of the ability to watch things on your own time.
Radio ads seem to be almost at a 1:1 ratio by now as well. I can't listen to the radio anymore because every time I turn it on I get obnoxious advertisements instead of music. Once again, they've increased the volume of these ads well above their music as well. So what did I do? I went and purchased a whole new stereo for my car just so I could hook up an iPod.
Ads are so annoying right now, that they're destroying their entire industry. It's so bad that people are spending large amounts of money on products that bypass them altogether. The guy who makes adblock, for instance, has made it into a full time job and survives off donations alone.
It works for youtube ads, Pandora ads, pretty much anything. It works so well that I am often momentarily confused when people complain about ads on a website, thinking, "But there aren't any ads there...oh wait, I have Adblock."