There seems to be some controversy on the point, although one study shows that there is very little actual blog readership cross-over between liberals and conservatives. Supposedly the number of conservative blog readers reading liberal blogs is smaller than the reverse, although by such a low margin of difference that would deny either side bragging rights.
Still, why might more liberals read conservative blogs than the reverse, even marginally?
Part of it probably has to do with the limited opportunities for liberals to even read or hear conservative arguments. Where can they be found? Blogs, talk radio, opinion journals, and from guest panelists on Fox News.
On the other hand, liberal arguments are the prevailing orthodoxy, and are pervasive in our culture. When Stevie Wonder makes a song out of Senator Obama's name*, are we really surprised? Liberalism dominates in the mainstream media, Hollywood culture, popular music, the arts, acadamia, and even popular television. If that wasn't enough, liberalism has an entire subsidized talk radio regime known as National Public Radio.
I myself find less time to read and to respond to liberal blogs than I have in the past, if for no other reason than I think the quality of liberal blogging locally has slipped in the last two years.
*Surprisingly Stevie Wonder couldn't use the Senator's middle name for the song. One would have thought the rhyming possibilities of "Hussein" to be near endless.