There's lots of talk at the moment about MMS traffic being lower than expected, and blaming this on ease-of-use. But, whilst I'm in no way making excuses for the operators, I'm not sure that this is the case.
Sending a photo from my Nokia 6230 takes 10 clicks, including going to the camera, taking the photo, saying "send by multimedia", choosing a recipient, and actioning it. In contrast, sending a text message takes 5 clicks - but *just sending a photo* will take way fewer clicks in practice, because you're not typing in the text of a message. So I don't think the problem here is purely usability.
Sure, composing a complex MMS that has multiple slides is more effort, and the language phones use for building this ("Add an object"?) isn't ideal; and believing that your photo might actually arrive does involve a leap of faith, even presuming that your handset has been set up to do MMS out-of-the-box (which many still aren't - WHY???). But the mechanics of sending a photo? I don't think it's tricky.