> Entering a restaurant that has salt on the table is nothing like me entering into a written agreement for unlimited salt from a salt distributor
What in Dropbox's terms of service do you think they're violating with this move?
Buying unlimited storage for common use fits into the paradigm of the not needing to be stated understanding on what unlimited means to a reasonable person. If you want to get more precise, the terms and conditions specify that Dropbox may, at its discretion, take various actions.
If I buy "unlimited salt" from a salt provider then I expect actually unlimited salt.
If I buy a meal from a restaurant and that restaurant provides complimentary salt on the table I do not expect unlimited salt.
Selling something as unlimited at a fixed price is clearly stupid unless there is a limit on the speed of the consumption (like the salt provider saying that you can have unlimited salt at a maximum rate of 1kg per hour or so). For something like dropbox it is even more stupid since every unit of product sold will increase their running costs.
You're talking about unwritten AND unverbalized social contracts.
Entering a restaurant that has salt on the table is nothing like me entering into a written agreement for unlimited salt from a salt distributor.