Luckily, not all companies choose Option B. (Or at least, not all at once.) This is the #1 reason I moved from AT&T to T-Mobile 3 years ago. On AT&T, if I went over, they charged a TON for the next small clump of data. I think my plan was $30/mo for X GB, and if I went over, it was about $15 or $20 for two-tenths of X GB more -- something ridiculous like that. And it wasn't optional -- if you went over, you paid.
On T-M, besides giving me more data for less money in the first place AND including tethering for free (which was also $15-20/mo on AT&T), they have no overage charges. If you go over your allotment, you get throttled to 2G speeds for the rest of the month. (Not sure if that is still how they work for new accounts, but I still have the deal that I signed up for.)
AND they were one of the first companies to make it easy to buy phones outright and not subsidize them, so if you can stand to use a phone for more than 2 years, you save money. AND they aren't jerks when you ask to unlock your phone. Etc etc etc.
Other than the fact that actual phone calls get dropped a lot more (like, weekly or more, versus almost never on AT&T), I've been totally happy with T-M and I've saved a lot of money with them over AT&T in the last 3 years.