1. Direct Marketing
Sending spam messages selling products on professional focused social networking sites. Yesterday I received an InMail on LinkedIn with a list of recommended holiday presents and links to purchase them from a fellow group member...seriously? How is this related to professional networking?
2. Inappropriate Jokes
Sending personal anecdotes or jokes to people you do not know personally. Such as the email I recently received featuring a picture of Tiger Woods beaten up and then below it information on a financial firm - do I need to say more?
3. Flame Wars
Writing disparaging and personally mean messages to other members in comment sections of networking sites (flame wars). If you don't agree with another member's opinion - show some class and share your opinion, don't take personal pot shots at the author or any other member for that matter - the only credibility questioned in these types of comments is yours.
4. Marketing Posts
Post products you are selling under group discussions. I recently saw an advertisement in an IT group I belong to under the discussions section pushing fictional books on tape - again how is the professionally relevant to developers?
5. Ignoring Your Audience
The reason you joined a social network is to have a voice. A message from another member should be responded to; they are listening to you, don't turn them away.
6. Post links to anything you are promoting on someone else's wall.
I recently accepted a friend request on Facebook from someone I barely knew and they actually posted a link to my wall promoting a book they wrote - needless to say it was quickly deleted and that person de-friended. Is my wall really a place for you to promote your book?
7. Posting Profanities
If an f-bomb is really necessary to get your point across, don't do it on a professional site and make your comments unsearchable. Keep in mind that prospective clients, employers, and colleagues are going to Google you. I am not judging you - but they probably are.