Photographers are always the subject of copyright infringement. If we worry about it constantly it will only disrupt our creativity. I use online proofing instead of giving hard proofs. Everyone has access to scanners so I decide to take my chances on online proofing instead.
I actually had a senior this year that was trying to demand proofs. I informed her straight up that the reason I don't do hard copy proofs is because I don't want to be ripped off. She wasn't happy. The same day she made the demand, I increased the visibility of the watermark on her photos. I prefer a no sale than a $100 order so she can copy my work.
On the other hand . . . I take hundreds of photos of sports and donate the digital images to the school for use in their yearbook without compensation. It is my way of giving back to the community.
Okay -- off my soapbox . . .
Point is -- if you post it online, chances are the images will be lifted. Some people could care less if there is a logo across the image and its printed on plain copy paper.