I actually think this is one of the biggest mistakes a lot of writers make - not spending enough time marketing their material. I'm terrible at networking in person but I have optioned and sold several scripts through cold query letters.
I'm someone who whole hardily does NOT believe in the old "write a great script and the rest will take care of itself."
Certainly early on in your writing career you need to spend your time writing, but once you've written 3 or 4 good scripts (which means probably a half dozen or so bad ones) I think you would be wise to spend a solid 25-50% of your time on marketing. I mean why not? If you've got some solid material why not push the hell out of it and get it out there to everyone who will read it?
Ashley at SellingYourScreenplay.com