My view is whatever you stick online will be stolen and may be used elsewhere. Mostly by individuals who just want to add a photo to a blog, forum, twitter post or whatever. However there are the odd few companies who seem to be unaware of copyright law, or don't care about it, and will steal them for their use. Some will try to claim they are non-profit so that makes it okay (no it doesn't).
Anyway, one way or another they'll try and if you can see the picture it can be copied, so don't even bother with javascript, flash and such tricks.
The only protection you can apply is to do as you say. The choice you have to make is whether you want people to see your photos more than be concerned about theft. If you have to make intrusive logos and such, then may as well not put them on at all.
I've had mine pinched a few times. One thing I do if I'm concerned is only upload 800 pix max photos on the web, so at least they're not much use for print. I'm also looking into ways of putting very small copyright in the photos that aren't intrusive but might get copied with the photo, or you can put copyright in the meta data of the image so it may be easier to hunt down and use in court should there be an argument as to ownership. Then again not uploading the original settles that as only you have the original, and meta data can be stripped off (though there are ways of embedding data in the actual pixels of the image itself in a hidden way).
It's a tough one. I'd say if there's something you want to make money out of yourself and don't want anyone else to, don't stick it on the Internet.
Thing is, I don;t want to ruin it when you look at the image - at the moment, the ones on the website were put into iWeb in full res, but on the website they're pretty low, I think you'd struggle for a normal size print out of them. 
