Definitely evil and unethical but probably not illegal. This post shows some insight into the issue but not an answer http://www.sportsandentertainmentlawplaybook.com/intellectua...
But actually using their product name in your ad as a link to your product page, the way GoToMeeting seems† to be doing here? That is very different. I think I would mistakenly click that link thinking I was going to MeetingBurner, and I am more ad-savvy than most Internet consumers.
† Note: I'm not actually going to accuse GoToMeeting of any wrongdoing here. Heaven knows I'd want people to wait for more than a TNW story before they indicted me. I'm just talking about the difference between the two instances.