Verizon's newest iPhone competitor, the Droid X, will come with an unlimited data plan for $30 per month. CNET:

The fact that Verizon is keeping this data plan is significant because AT&T. . .  has eliminated its unlimited plan in lieu of a new two-tiered offer that caps monthly data usage. Now it looks like Verizon is using AT&T's pricing shift as an opportunity to pick off consumers, who may be interested in the iPhone 4 but are scared off by AT&T's change in data plan.

Maybe this move by Verizon will also stabilize the shift to tiered data plan pricing in the UK, which appeared to be precipitated by AT&T's move to tiered pricing.

Will AT&T hold steady or back off?