There's an interesting interview with Neal Stephenson (author of Cryptonomicon) on slashdot. The answer I found fascinating was the second one - a discussion of popular vs. literary writing.

Do you think fanfic counts as Beowulf writing?

Mere

I would say most fiction written these days does. Authors like Stephen King who started while they were still in their day jobs, but later became successful enough to quit them, are more accountable to their fans than anyone else. It is the readers who really decide what has value.

Stephen King, although he has a great deal of talent, has been sneered at by literature purists because he writes genre fiction. But does that make his stories any less interesting to read? Does it make him less of a writer? I don't think so.