Multisite, shared users, own databases, own files, how to deal with profile picture? I'm in the middle of implementing a multisite setup. Each site will have it's own database, and files directory, but they will share the user table from the default database.

Because the profile picture field in the user table is set to a fid, am I right in thinking this will break a user picture if they look at their profile on a different site?

fid 26 might be their picture on the main site, but fid 26 in another site might be for a completely different image, or not even an image at all.

How do you normally address this issue?

Cheers
You need a single sign on approach.
You could implement your own approach just like this one https://drupal.org/node/1043724 or try to find some contribute module to handle it.
Hope this help.
Regards