Search: happy birthday
Why: You know what's a weird song to have stuck in your head? "Happy Birthday."
It's famously annoying because a) everyone knows and uses the song in real life, b) it's copyrighted, and c) the royalties are absurdly expensive for such a dumb song. Because of that, we end up with tons of scenes like this:
Answer: 2030! In the US, anyway. In the "EU," the copyright will expire in 2016. The rights are held by Warner/Chappell Music.
Source: Wikipedia, Yahoo! Answers
The More You Know: According to the Guinness Book of World Records, "Happy Birthday" is the most recognized song in the English language. The reason the Guinness World Records thing started was to settle bar bets. The first question Hugh Beaver, managing director at Guinness Breweries, had was:
Which is the fastest game bird in Europe, the koshin golden plover or the grouse?Answer still unknown.