I hate unlimited plans. Well, more accurately, I hate “unlimited” plans. “Unlimited” is a euphemism for “more than you’ll probably use”. It’s a plan with a lot of headroom, but you don’t know how much until it hits you in the pants.
Let’s take “unlimited” broadband internet access. For something like $40/mo, you have one plan to pick from: “unlimited”. You get something like 2 Mbps, for the month. But what would happen if you actually used that? 2 Mbps constantly for a month, would be about 630 GB. You can bet your pants that they’d cut you off if you did that, or even came close. Although a lot of people don’t hit the limit, it’s there, somewhere. Lurking in the shadows.
All iPhone data plans are unlimited. Yeah right. I once worked with someone who had “unlimited” text messages, and within a couple months they pantsed her for using thousands. Unlmited my ass. The problem with the unlimited iPhone data plans is that besides not knowing what will get you cut off, the infrequent data users are paying for the hogs. If my mom wants the iPhone because it’s pretty and a good iPod, she can’t get a cheaper plan even if she uses only 1MB a month.
This is sort of like an all-inclusive resort. A lot of people swear by these things. At all-inclusive resorts, everybody pays the same amount, and gets unlimited food and drink. So you have your dinner and 5 drinks, which are a little watered down, but hey, it’s unlimited. 
Meanwhile, you’re heavily subsidizing the lardo who can eat 4 steaks and drink 23 margaritas. Then, you get to spend your night around a guy who drank 23 margaritas. He vomits on your pants, and you wonder why you even need unlimited data in the first place. I mean, unlimited margaritas.
Almost as bad is having a limit but not enforcing it. How many highways have a limit that is universally ignored? The posted limit isn’t the real, unofficial point where you’ll get a ticket. Just post the real goddamn limit people. When I worked at an ISP we did this - the limit was 10GB/mo or something, but we never enforced it unless somebody went totally crazy. The problem is, those poor kids never knew just how crazy they could get until the pantsdown came.
Our Dreamhost does this right. They offer huge amounts of bandwidth and space, “overselling”. Recently, though, they decreased these amounts for new signups - which is awesome! They still offer 150GB of storage and 1.5TB of bandwidth for $7.95, so it’s still a great deal. And obviously, almost nobody ever comes close to the maximum. So, you have more peace of mind that you’ll never hit the limit than if you were on one of those supposed “unlimited” plans that have a hidden limit. Plus, you know that nobody is trying to serve an unlimited number of pantsless Jessica Alba photos off of the same server that Altering Time is on. Although, I guess that would be pretty cool come to think of it.