Can you save/cache API data into your own database?

Trying to get a handle on how these things work.

If I register an API key with Twitter, Foursquare, or Facebook, and I wanted to build an app on top of them. 开发者_开发百科What are the general rules for API use?

Can I save/cache data a user allows me through oAuth to my own database, or am I only allowed to use it but not keep it?

I don't know about all APIs, and you should probably read the terms of service of each API you'll use.

Saving data you'll frequently need will decrease requests you'll have to do to each API, which they will be thankful for, so it shouldn't be any problem. However, it is possibly that they require you to erase saved data if the users revoke access to your app, etc.