How Social is Your Network?

After receiving yet another "invitation to join my network" from Plaxo, Zing, Zoom, Boom, et al... I wonder just how many social networks are too many? If I spent all my time joining networks, posting and updating bloggs, and attending networking events, there would be no time left for recruiting. This conundrum makes me wonder if all the really great, prolific bloggers out there are strictly in management, independently working or do they stay up late into the wee hours of the morning updating and posting?