You share information and expose your community to your interests so, promote proper etiquette. The guy or gal who adds anyone is an example of improper use of Social Media. The concept is to create a community with similar interests for discussion and let the popular opinion grow your visibility. You may belong to several communities and you may have some of the same friends, that’s fine. Remain active in your communities by adding friends and contributing relevant content. Bulk adding friends, for no reason, is not good etiquette.
Communal sites are popularity contests. Trying to catalog massive amounts of unrelated friends is totally counterproductive. For the purpose of social media, you should concern yourself with quality, not quantity.
Using unsavory techniques is equivalent to spam and social media spamming is more atrocious than email spam, because the offending text is visible to everyone on the site. If you don’t have something relevant to say, don’t say anything at all.