Like Facebook, Twitter is essentially a communications tool.  But unlike email and chat, what Facebook and Twitter (as it continues to grow) are also navigation tools, look at the Top 10 beneficiaries of Twitter’s surging traffic:

And here is the trendline for each:

Twitter’s growth has been nothing short of spectacular, but I repeat what I said: Twitter is 2009’s version of Facebook… and before you know, I predict Crapstr will come along and steal Twitter’s thunder in 2010.