Yes, it is. There's a reason why Knuth answers regular mail as a batch process (once every few months), for example. A common productivity tip is to limit yourself to checking email only a few times a day. The productivity harm caused be frequent context switching has been well-documented, especially if you're doing something context-intensive like programming.

But you don't have to deal with e-mail as a dribble, as you say. I deal with e-mail as a batch process, just several times a day instead of once every few months. Ditto for Twitter and the like.