Naturally, Verizon targets T-Mobile's limited 3G network. By the end of 2008, T-Mobile will have only 27 markets with active 3G up and running. Verizon Wireless' 3G footprint is vast.
Other features that Verizon targets include the G1's limited on-board memory (128 Mb), lack of support for Microsoft Exchange, no ability to provide turn-by-turn directions, lack of stereo Bluetooth and video capture, and the G1's limited ability to purchase music over the air.
Verizon also takes a stab at the Android Market, saying that it has no guidelines for quality, usability, interface, or performance for applications.
Finally, Verizon makes sure to point out that the open operating system provides ne'er-do-wells with more than enough opportunity to breach the security of the G1. That's sure to push the buttons of IT admins.
My guess is that people who are interested in Android and the G1 are not necessarily the type to buy a BlackBerry smartphone.
Incidentally, in December 2007, Verizon Wireless said it would welcome the Android operating system to its network at some point.