Say I had an open-source project which I wanted to try and generate some exposure for. Would it be considered unethical to set up a project entry for it on several sites such at github, sourceforge and google code, for example?
This would be purely for giving it greater exposure. I realise there might be some practical reasons for doing this, such as wanting to use github for source control, and sourceforge for issue tracking, forums and such. For the sake if this question I'm wanting to focus more on the case where you use one of the sites as the main site for the project, and make "stub" projects on the other sites that point back to the main site.
My gut feeling is that while it may not be outrightly unethical, it might be bordering on the sleezy side...
Stick with one provider. "If you build it, they will come" :)
Besides, once people do start coming, they'll just google the project name anyway. Finding the same project on Sourceforge, Github and Google Code is just going to annoy the hell out of people.