[All the reasons @Chopper3 gave][1] are still valid ones:

* The actual authentication process is secured over SSL/TLS.  
  (at least if your OpenID provider isn't made of *suck*)  

* Everything else you do on ServerFault is public<sup>*</sup>

* Adding SSL to StackExchange sites is computationally expensive  
  (Good enterprise SSL accelerators range in cost from about as much as a pony to about as much as a house!)

<sup>*</sup> – *Possible Exception*: Associating email addresses with your account & subscribing/unsubscribing to site newsletters.  
I agree that *these things* should probably be happening over SSL if they aren't already.


  [1]: http://meta.serverfault.com/a/1793/32986