• good AT&T will FINALLY allow data tethering via the iPhone, after blocking it for years.
• bad AT&T will no longer offer unlimited data plans, but instead two tiered data plans.
• okay Old customers won’t be forced to switch, but new customers will have no choice.

The new charges

• $15the cost per month for the 200-megabyte “DataPlus” plan; it’s $15 for each additional 200 megs
• $25 the cost per month for the 2-gigabyte “DataPro” plan; it’s $10 for each additional gigabyte

The bullet points

• » Why do this, anyway? Because AT&T found in its research that most customers only used a certain amount of data, and a small number of users accounted for most of the bandwidth-sucking data usage. Take that as you will, kids. On the plus side, AT&T is at least trying to make the new charges somewhat friendly to consumers, allowing for retroactive changes between the two plans.
• » The wildcard, of course? AT&T is the first company to do this. Which means that Verizon, Sprint, all those other companies? They still have unlimited data plans. And if Verizon gets the iPhone like is being predicted, it seriously puts them at an advantage. source