It's a breach of the law
Your T&C can say what they like, but if your ADVERTISING made a clear offer then that advertising overrides your T&C, unless you engaged the Big Red Hand. Contracts, esp consumer ones, are based on total package of communications.
So, yes, they can change their prices at any time, for those that joined before the offer or after it, but NOT for those who had a reasonable expectation of a year of unlimited storage. (Note, while the word unlimited might be held to be puff, anyone in the target market backing up target market type stuff should be fine).
If Monster is consumer oriented, how about a Your and Yours story, (and at the same time educate some journos on tech).
Biting the hand that feeds IT
