First, I understand one phone is usually a personal line and the other is for hobbies and such... so this post is more tongue-in-cheek than anything else (though it might be informative for providers who aren't aware of what I'm about to "reveal")...
Google Voice!
Considering they let you choose your area code, number, when it's on/off, text you transcripts of voicemails if you so choose, along with the ability to change your number as much as you see fit while at the same time letting you receive and make calls on your "virtual" telephone from your real one (over the data connection), it's hard to see why anyone wouldn't have it! Yes, that was a run-on sentence, no, I don't care. I have one for my work and it simplifies the hell out of life in general, to the point that I feel sorry for my counterparts who carry around a work phone and personal phone... Though as a guy, that isn't easy.. Girls have the luxury of purses so I guess it isn't as bad (though I guess if they really wanted to, guys could go Euro and carry a man-bag... or not).
Anyway, I'm done with my random and completely pointless monologue. Thoughts?