The real carrot for me was the idea of a prepaid $29/mo data only plan, which I actually thought was believable. T-Mobile already offers pretty much the exact same plan ($1/day) for prepaid Sidekick users (voice is 0.15/min.) I barely use voice (~100 minutes/mo), and if I could drop my unlimited text/internet/450 voice plan for something that was only $29, I could definitely learn to live with the quirks of VOIP on a mobile handset and the loss of MMS.
Honestly, even if you threw me in a contract to get the phone at $199, as long as data was that cheap I'd gladly sign up for two years the same minute I was sending Verizon their $350 good-bye letter.
I don't use my phone as a phone and am sick of having to pay so much for minutes I just don't use. The cost of my voice plan before data and text is around $40/mo, which works out to me paying .40/minute for what I use. Even if I used real voice instead of Google Voice I'd be saving money.
Not to mention at that price they'd be dealing Apple a major blow. I figure they have the cash, why not use it for something like this. I admit this is all idle speculation on my part, and that Google may or may not have a lot at stake in the success of Andriod.