You can buy from Verizon too as long as its retail and not subsidized I bought one of the nexus they had on sale for $229 at retail and I still have my unlimited only subsidized phones they make you change your plan
I have several upgrades. I could upgrade, say, grandma's basic phone to a new smartphone at Verizon's lower price (have to activate on grandma's line). Once activated, move that new smartphone to my unlimited line and put her own phone back on. You will have to reactivate with asterisk 228 to reactivate grandma's phone. Get the full 1 year warranty, can add insurance and keep my unlimited data. Or buy the Nexus online or used in EBay, Craigslist, wherever. You just can't have insurance or warranty if you buy used (unless phone is less than 1 year old, you still have warranty).
@keepitreal, when you move the new 4G smartphone to your line you have to go to the corporate store, right because they need to give you a new sim card for the unlimited data phone? And since you are at the corporate store you can have them cancel the data plan on grandma's line right? I need to get this story straight because I'm about to try it (boyfriend wants that new HTC dna phone).
Fyi, two years ago I bought a used droid x from a friend and I had I insurance on my previous moto droid weirdly enough my insurance covered the droid x when I lost it three months later... My point is this that insurance once you have it covers any phone you place on your line (I'm currently still being charged and I got my nexus from eBay).