Last month my wife went over her data allotment. She normally uses about 500 MB a month for email, the occasional web site and maybe an address lookup. How she racked up 2.5 GB of usage in a couple of weeks is a mystery, but it's not unusual. Leaving just 1 app open can suck up all kinds of data without notice...until it's too late. I don't know if a 10GB limit would have kept her data alive. Now that all of the top 4 carriers offer unlimited data, should she consider an "unlimited" plan? We can see how some of us really want an unlimited amount of Data, not necessarily to use, but "just in case."
Fortunately, there are alternatives to unlimited data for those of us who go over our data limit only once in a while. Our favorite alternative is "throttling". Until now, I never really gave much thought to carriers that "throttle" their data over your limit, but I now see what a great advantage it holds over those that brick wall your downloads. With throttling, when you hit your maximum, your download speed goes from mega-bits to kilo-bits. There is more than one of the smaller carriers that only drops you from 4G to 3G...would you notice? Even at 2G (128Kbit/s) you can still use a map or read your email.
The next option are the carriers that offer an extra GB or so for an additional fee. If you have a hard data limit or you truly want more high-speed data over throttling, the extra data charge is a good deal...if you only use it every few months. It's certainly better than paying a high monthly fee for unlimited that you may never use. My wife has the patience to wait until she's back on Wi-Fi, but she'll re-think her next plan to consider one that throttles instead of one that cuts her off. It's nicer that way.