Sure, it's basic golf etiquette not to use a cell phone on the course ... you should turn it off or to vibrate and only take a call that's an emergency like Thumper says, but people are idiots. It's just like the movies - people are so used to watching DVDs at home and talking to each other, replaying it or fast-forwarding, stopping for a bathroom break - it's so bad that it's hard to enjoy a movie in the theater anymore. Someone is always talking or making noise.
If anyone wants to secretly confess to a breach of etiquette, there is actually a website called the Golf Etiquette Confessional ... not a lot of postings yet, but it's sometimes good to see that others are doing things they shouldn't and feel bad about it later

Here's the link:
http://www.mrgolf.com/confessional.html