Hi everyone. I spent about an hour with an AppleCare rep (Jeremy) on this issue last night and he said he had no documentation about this. Took me until this afternoon to find this forum, so I thought I'd throw an extra note up here to add my story.
About 3 days ago I upgraded from iPhoto '09 to '11 (v9.4) and had an issue where iPhoto would crash when uploading to Facebook. Removing / Adding my Facebook account into within iPhoto helped a little but didn't keep the program from crashing. A call to AppleCare helped find the fix: removing the iPhoto-related .plist files in the Library folder.
Unfortunately, that didn't fix the issue with the 25 picture limit. I tried uploading a new album with 80 photos after deleting the plist files, and during upload I could see all 80 photos listed in the Facebook album within iPhoto. As soon as the upload was over, the album suddenly changed to only 25 photos (but all 80 are visible on Facebook's site). Jeremy recommended I send feedback through apple.com/feedback, so we'll see if they contact me like Jametait. Thanks for posting this thread!