In my case it is DLS that has these limits.
I think we’re about to see collusion at its worst as they all implement caps. The key will be to continue to watch the market, negotiate the best deal, and be willing to switch as needed. I’d expect something similar to the cell phone business where you lock into a certain rate for a period of time. For email I’d switch to an ISP-insensitive service like gmail so that as I switched providers there would be no email address change to deal with.
I would think that the advertisers would scream the most as there would be a distinct rise in ad-blocking software - why pay to get ads? Not me...
Oh well, my $.02