Allow me a moment to urge you all to read Michael Turk's diary today on GOP Online Politics and Internet Regulation. Turk knows of what he speaks on this front, and I agree with 90% of his argument on the falseness of an access gap.
I would add that there is one significant demographic factor that I do believe hampers Republican efforts online - not top-down efforts, but grassroots ones. Namely, what is striking about the sociological difference between the average Daily Kos reader and the average RedState reader is the consistent and vast gap in the number of children in the home. The netroots consistently appear to be older than you might expect, with children out of the home or in college, while a large percentage of our readership - and the readership of other blogs on the right - consists of parents with younger children in the home, and larger numbers of children.
This is not a significant enough factor in terms of explaining the current gap, but it is a factor. For an example of how this played out in politics before, one need only look back to the 1990s, and the rise in participation from evangelical families on the right. Having a family takes priority over grassroots politics, as it should - and it makes you slower to respond to the daily grind of political activism. But the good thing is, of course, that you end up with a lot of free volunteers on election day.