When you become a member of some website, you look it over, you weigh the advantages and disadvantages, and maybe after reading their various policies (ok, probably the majority of the people doesn't read them) you decide to sign up.
You do that with the website as it is at that moment.
If at a later date the website owners decide to use the data that you gave them under your previous image of that website in new, creative and unexpected ways they are effectively breaking the unwritten contract between their users and themselves.
This will usually cause a backlash, but only in a small portion of the userbase because most sites are too small to get significant mainstream press coverage.
When sites like facebook get involved in this sort of thing the media will latch on to it immediately because of the potential audience for the information. This will then piss off more people that otherwise would not even have realized something has changed and so on.
It's a side-effect of the network effects that facebook profited from when they established themselves, I don't think it is possible to have the one without the other.
You do that with the website as it is at that moment.
If at a later date the website owners decide to use the data that you gave them under your previous image of that website in new, creative and unexpected ways they are effectively breaking the unwritten contract between their users and themselves.
This will usually cause a backlash, but only in a small portion of the userbase because most sites are too small to get significant mainstream press coverage.
When sites like facebook get involved in this sort of thing the media will latch on to it immediately because of the potential audience for the information. This will then piss off more people that otherwise would not even have realized something has changed and so on.
It's a side-effect of the network effects that facebook profited from when they established themselves, I don't think it is possible to have the one without the other.