From the Pew Internet & American Life Project:
Internet users have somewhat larger social networks than non-users. The median size of an American’s network of core and significant ties is 35. For internet users, the median network size is 37; for non-users it is 30.
This survey (PDF) concentrates on email being the main Internet social glue, but it’s worth noting within the context of e-learning. People who use Internet tools for communication have a larger core social group; in education this means a larger number of people to discuss, share ideas and learn together with.
I think this bit is also important:
Contrary to fears that email would reduce other forms of contact, there is “media multiplexity”: The more contact by email, the more in-person and phone contact. As a result, Americans are probably more in contact with members of their communities and social networks than before the advent of the internet.
In other words, using Internet tools to communicate is not going to preclude offline methods of communication, which hopefully will put to rest some fears about e-learning tools (and use of the Internet in general). In fact, the survey can be read to suggest that they will be beneficial to outside social interactions.