Adding ResearchGate profile to Resume? It is common that people add their LinkedIn profile in their resumes. On the other hand, they add profiles (like ResearcherID) counting publications, citations, and showing factors such as h-index.

ResearchGate is something in-between, but I have not seen if anyone add his/her ResearchGate profile link in resume. Is it because ResearchGate is young and not popular, or it is not technically convenient?
I think the reason ResearcherID is sometimes used on CV's is because it's a quick way to link to (and host centrally) your publication list as well as bibliometric information (h-index, number of citations, etc.). I also see people use Google Scholar as an alternative service for that, although the quality of citation data is not as good.

For LinkedIn, it may be field-dependent. I see a large number of people around me (chemical engineering, both academic and industrial) semi-actively using it, i.e. maintaining a network of peers and getting the occasional introduction/reference through it. I do not often see it used in CV's, however. It is clearly used for networking.

ResearchGate, as you stated, is neither here nor there. It's not very widely used yet, and rather aims to be a "Facebook for researchers": it is centered around papers, comments and discussion. While it can be used to host a publication list, the metrics it offers access to are not commonly used and, one must say, rather opaque. I think that's why it has little value to add to a CV.