Buying unlocked....

Could someone spell out to be what the benefit is of buying a phone un-subsidized (aka unlocked)? I'm a Verizon customer, going to be getting a new Android phone in the next month or two. I'm pretty sure my family is on the 'share everything' BS now since they virtually mandated it a month or two ago. The only benefit I can see is that I would not be locked into that phone for 2 years and (possibly?) get unlimited data.

I will surely be getting a Nexus (assuming the new flagship comes to Verizon), so if anyone could give me a rundown on buying unlocked, I'd appreciate it.