I love it when people question the way I build my social networks.  "Why would you want to be friends with so many people?"  "How can you keep track of so many?"  My answer, always, is simple.  Why not?  It's good for both business and personal networking. 
You don't have to actually interact with, or track, everyone, all the time, in your networks on Facebook, Twitter, etc.  You can easily categorize people into groups or lists to keep track of them, and segment them within your social platforms.  I target who I connect with either by location or by niche interest.

I have always believed that bigger is better when it comes to networks, especially if you are efficient at targeting, tracking, and communicating.  The main reason for this, for me, is SEO (search engine optimization).  How do I rank in search results on Google for my name or my niche?  Everyone in business should be concerned with this.  Now we have one more reason to know that size does matter.
Today Christopher Penn, VP of Strategy and Innovation at Blue Sky Factory, posted an article on his blog detailing how Google now adjusts search results on a per-person basis depending on the searcher’s social connections.  So if you follow me on Twitter or Facebook and search for "social media speaker", or "Linkedin training", Ajax Social Media and Fishdogs will appear higher in search results than if you didn't follow me because I share stuff from those brands on my Twitter and Facebook.
This is a fascinating shift by search engines and will be important for anyone looking for drive more traffic for business. 
One thing is important to keep in mind when building your network: engagement.  If you aren't sharing good content, and replying to/promoting/helping others, your network will start to show the results of an empty shell and will disintegrate. 
Build it.  Feed it.  Rank higher in search results.

Social media now directly influences search rankings
by Christopher S Penn
In a recent stunning article, SEOMoz highlighted that Google’s search results are now being adjusted on a per-person basis depending on the searcher’s social connections...
full article here