Should "Happy Birthday" be Protected by Copyright?

PBSIdeaChannel:
You know how chain restaurants always sing some weird unknown birthday tune, instead of the actual Happy Birthday song we know and love? It's because "Happy Birthday To You" is protected by COPYRIGHT!!!! They are legally not allowed to sing it in public, and neither are you. Copyright was originally created for two reasons: to protect the original creators so they could benefit from their work AND have creative works enter the Public Domain. Unfortunately, the whole system has gotten out of whack with copyright extensions that extend far beyond the life of the creator. The current holder of the Happy Birthday copyright is the Warner Music Group and the original creators of the song stopped having birthdays a long time ago because they're dead. It makes you wonder if copyright law hasn't deviated a bit from it's original intentions. Or maybe you just shouldn't celebrate your birthday in a Red Lobster.