In life we can not always exert control over our social network. You can have a private phone number, yes, but telemarketers can still get the number often times. You can allow calls to go to your answering machine or not answer but you will still have to hear the phone ring.
You can have spam filters and such set up on an email address but you can not necessarily control who emails you. Email lists are often sold, despite what anyone might say about “not selling the list”. Further unless you are a better person than I and can avoid responding to emails you can not control who emails you when.
In social networks you can typically choose who friends you and who doesn’t – but with services like Twitter you can’t pick who follows you and who doesn’t unless you private your account which often leads to few following you at all.
The great advantage to having your own instant messaging network – from a service such as Brosix (check out http://www.brosix.com for more information on the service) – is that you can pick and choose who is on your network and therefore pick and choose who can contact you.
That is why I recommend products like Brosix to businesses!