Looks to me that the answer is no.
I went into iphoto (06 for me) and looking at my Halloween pics for a gap in file numbers, then searched in finder for the missing file, and low and behold the missing/deleted file is still listed in the original and thumbnail/data sections of the iphoto library. Doing a search for the missing/deleted file in iphoto turns up nothing. Both the iphoto trash and main trash have been emptied. I can open the missing/deleted file found in the Finder with Preview.
If anyone can explain this, I would like to know. This could be the reason people think their iPhoto libraries are exceedingly large--because you can't really delete? I know I take a lot of soccer pics using the drive function of my camera and end up with a lot of garbage shots, that I guess aren't really getting trashed after import.
Link to iphoto support in Apple forums:
http://discussions.apple.com/thread.jspa?messageID=8269872?
Ok....I did more searching for gap/missing/deleted files based on the file numbers, and most of the latest searches turn up nothing, as in once deleted, they stayed deleted; I don't know what the differences are.