As usual, I agree with Durant. I'm happy to accept anyone wanting to be in my network and all are welcome (I only have a few at the moment). In the world of MySpace, Facebook, and others like it, it's just another way of "networking" - connecting with people in cyberworld.
When I go to conferences or meetings, I always bring business cards and pass them out. Cyber networking is the same - maybe something will come out of it, maybe not. In any case, you don't have to "do" anything else (nobody expects it either). Most people leave you alone, so you're not going to be bombarded with stuff (or spammed). If there is any odd behavior, then you report it and dump the person from your network with the delete key.
I just check to make sure someone is legit on the site before accepting. It doesn't matter if they have done it for ages or are just beginning. We already have the common thread as writers.