AMum provides some very good examples of how photos are useful, and there are others throughout this thread. Not being able to appreciate this shows quite a lack of imagination. Wowfudge in your original post you said that people visiting from other offices 'seek out people the deal with and introduce themselves'. How much easier would that be if you already knew what they looked like? Rather than have conversations like:
-"do you know where wowfudge sits?"
-"umm I don't think I know who wowfudge is, I've not worked here very long, can you ask someone else?"
-"I think it's that lady over there, but actually maybe I'm confusing her with someone else?"
Instead they might just pass you in the corridor and say "hello - wowfudge isn't it? - I recognised your face from the intranet, nice to meet you in person at last! I was just thinking about this amazing project we've got coming up, perhaps you'd be interested...?"
Not so complicated is it?
As for the information being abused, yes it's possible. I presume you have your name, phone number and email address on the intranet already. In which case how often have you been:
-subject to rude limericks using your name?
-the victim of prank calls using your phone number?
-signed up to dodgy spam emails using your email address?
Probably not much? I expect it'll be the same with your photo. It's not a high risk and it would of course be a disciplinary measure if anyone abused it.
Which just leaves just not liking your appearance/not being comfortable with your photo, which is just a bit petty I'm sorry. I hate they way my voice sounds recorded, I still have a recorded message on my voicemail. My handwriting is embarrassing but I still write notes for colleagues. We just have to get over ourselves to get on with work.