YouTube

YouTube has become a huge outlet for advertising. It's actually just become huge in general. It's where EVERYONE goes to see ANY online video. I couldn't really name a serious competitor. All the ads referenced in my Intro to Advertising course came from youtube. Tosh.0 is a television show created entirely to find and make fun of some of these videos.
It's an excellent place for companies to post an ad, for a couple of reasons. Number one being that it's free. You just gave over 300 million people access to your message for FREE (although it comes at the cost of clutter, 200,000 videos are uploaded daily). Number two being that the people who watch an ad on youtube, WANT to see the ad. They are much more likely to listen, watch, and receive the message. While the internet audience doesn't represent the masses, many companies are taking advantage of this medium, from AllState to DieHard.

Below is a really cool video from DieHard, catered to the internet audience.


Additional kudos to DieHard for making the ad entertaining. Many companies simply post their TV ads; without the entertainment value, fewer people are likely to actively seek out the ad.