Today while researching a story on social network sites, I came across this MSNBC column by Eve Tahmincioglu, discussing the frustration of wading through the maze of social networking sites available today.

Here’s what people have been asking me lately: “Is it enough just to be on LinkedIn and Facebook?” “I just got an invite from a friend who’s on Plaxo. What is it and should I join?” “Will I dilute my networking effectiveness if I’m on MySpace, LinkedIn, Facebook and Twitter?

With so many social networking sites out there - and more on the way - how do you manage them? Do you focus on one or two, while ignoring the others? I haven’t seen any research along these lines, but I’d be willing to bet that the majority of users tend to put most of their networking energy into one particular site.