There's no way you can prevent copying and printing on internet. I'm familiar with dozen ways to protect your image and none of them work if someone is a professional in web-technologies.
That is likely true, just as it's true for cars, houses, etc. Security comes in layers and just because you can't stop the one guy who can get through five layers, that shouldn't mean you don't put up any security at all. My experience of people using my images is that they know nothing about rights. The Internet appears to them as a free-for-all. When confronted, they learn something, and they stop doing it. Personally, my only real concern is that I don't lose rights that way. For me, and I suspect most of us, our pictures are not likely to be stolen and used to fund a new yacht for some cyber crook.
That said, back to the topic at hand...
After trying a few different hosting sites beginning a few years ago, I finally dropped just about everything except Smugmug. As I've often said here I take pictures only to satisfy myself so I don't care if anyone else looks at them or likes or dislikes them. Neither Smugmug nor I provide any promotion. It costs around $60 per year to get a lot of options; costs vary with service level. I can copy-protect on a gallery basis. I can make galleries public or not. I can share images in various ways. An activist group asked me to take some pictures at an event recently so I created an unlisted gallery (anyone with the URL can see it) with no copy protection. They can view and take/use the images for whatever they like. In such a case, I relinquish copyright; it's like my contribution to their cause. They also have nothing that limits me -- no file size limitations that might affect me and no bandwidth restrictions. I can link an image here, for instance, and within a day or so have thousands of views on that image.
Once in a while I'll post something to Flickr, but I've never cared a lot for it. The real value seems to be in the various groups. For example, I get to see some great pictures of great architecture in the Louis Kahn group:http://www.flickr.com/groups/louisikahn/
I don't have to contribute pictures to the group, but as a member I can contribute to conversations. If anyone is interested, by the way, I'm looking for pictures of the new Four Freedoms Park in New York City to be posted there. It was designed by Louis Kahn and just opened a few weeks ago. The photographic possibilities there seem awesome (a word I don't use as lightly as some). A lot of the groups I've seen at Flickr tend to have tens of thousands of members, some with hundreds of thousands of images -- so a lot of it seems real impersonal to me.
I've looked at, even participated in some of the more artsy sites -- Red Bubble, that 500 group that's been mentioned. I felt mainly lost and out of place there. Most photographers there are way out of my league.
For a while I contributed pictures and picture essays to the JPG Magazine site. It's largely amateurish in my opinion, and I didn't like the social media aspect of it -- a circle of "friends" all telling each other how magnificent their mostly mediocre images are. When management quashed something I published they did not like, we parted ways. The real loss for me was the ability to do photo essays, a form I like. I don't know anywhere else to do that.
Once in a while I'll post an image to FB if it helps some cause I'd like to advance. Most serious photographers I know don't like what FB does to their images (compression, etc.). For me, there's a lot to not like about FB.
Anyway, thanks for asking.