I got a great note from someone today that was very much on point about what she described as a social media "faux pas..."  - I'll let you see it in her words (identifying details of the company/group in question have been removed as they've probably already suffered enough...)

These people make message t-shirts with cool phrases that ###### might like.  They obviously sent Friend requests to people who were Fans of ######.  I was annoyed by the unsolicited commercial Friend request- probably other people were too.  BUT- had they joined the group and posted info/links to their website and INVITED people to become Fans, they might have been more successful and less intrusive...  Finding ways to "attract" rather than "intrude" is generally a much better approach.

Making matters worse, they had registered their company name as if it were a "person" in Facebook, which is another way to really annoy legit users.

I do get asked a lot about online etiquette, and I think a lot of the advice I've seen sort of complicates the matter.  I just try to treat others as I would like to be treated, whether online or off. Here are a few cardinal rules I follow that I hope will be helpful:

1. Ease into it.

Spend some time in groups and on sites before you start contributing, so you can get comfortable with them. Just like in offline life, every clique has its own way of communicating, and ignoring the local customs is just as rude online as anywhere else.

2. Talk about other people more than you talk about yourself.

You can demonstrate your knowledge and credibility by what you share. Don't make it a one-sided conversation.

3. Help people out.

Share things that will make their life easier or better, whether it's a way you saved some money or time, or just a positive thought - we can always use those, too.  I follow a local PR professional who shares lots of great insights. But the best thing I ever got from him on Twitter? A warning about a huge traffic jam on the way to an event I was attending that night. I took another route and saved about half an hour of stress, and couldn't thank him enough for the assist.

4. Regardless of the platform, just be cool to people.  

I think of Facebook as the world's biggest cocktail party. Nobody appreciates a shameless self-promoter at a club - why would they appreciate them online? If, on the other hand, you get to know people, share quality ideas and (non self-serving) information with them, and develop a relationship, you'd be surprised at the doors you can open. If in the end you create a business result, that's great. But you might also find yourself with a lot of new (real) friends!