Lots of places do this if they have free wi-fi. I think Denver Airport does it (or used to). The Portland city wi-fi thing used to do it. It's annoying, but they have to make a load of cash rather than actually just charging me a few bucks, amirite?
I'd pay $2 to not have to deal with the hassle those ads cause. Easily. And that'd surely be more money than they're making off of me with them.
You should follow the guideline to post the source not from the news site.
http://ycombinator.com/newsguidelines.html