Normally your data is gone, except the service was sold to another company who will continue operations.
Let's have a look on Facebook:
The Company reserves the right to change any and all content, software and other items used or contained in the Site and any Services and Platform Applications offered through the Site at any time without notice.
The Company may terminate your membership, delete your profile and any content or information that you have posted on the Site or through any Platform Application and/or prohibit you from using or accessing the Service or the Site or any Platform Application (or any portion, aspect or feature of the Service or the Site or any Platform Application) for any reason, or no reason, at any time in its sole discretion, with or without notice
And even if your life ends, your FAcebook account will be still alive:
When we are notified that a user has died, we will generally, but are not obligated to, keep the user's account active under a special memorialized status for a period of time
You can like it or not, but once you checked "I agree", it's a little bit silly to complain.
What about Flickr?
First of all, Flickr is a PUBLISHING service, not a STORAGE service. If you don't back up your pictures, it's your fault.
Second, if Flickr is closing the portal (tehy don't mention this in their Terms of Service, but Yahoo does):
You acknowledge that Yahoo! reserves the right to log off accounts that are inactive for an extended period of time. You further acknowledge that Yahoo! reserves the right to modify these general practices and limits from time to time.
Another way to understand is common sense. Imagine a friend wants to stay in your house over night. Of course he will not charge you for the night, but you will also not expect to have a breakfast buffet and a maid. So companies like yahoo do the same, the offer you a free service, get some advertising revenue for this, and you can use the service as it is. If you want more, its not free anymore.
It's funny to see that people always complain about a free service. If you don't like it, just use another or set up your own. It's like the overnight stay: You will not use your friends underwear just because he invited you to stay in his house.