I'm not suggesting they should be forced into anything, and I don't have a problem with the idea of a person using a central hub; I use google applications for tons of things, for documents, calendar, etc. What I don't like is that to communicate with anyone using the facebook hub, you have to also be using it. I can use nothing but gmail for my communications, but someone using hotmail can easily communicate with me.

An equally serious problem is that Facebook makes no assurances whatsoever about whether they will choose to filter/censor communication (as they did here http://techcrunch.com/2010/11/22/facebook-censorship/). If I/a business want to be absolutely sure that any mail sent to me will get to me and never be deleted or censored, I can buy a domain and run my own email hosting; it's not a the whim of some external company.