As far as I can understand, the WGA are striking not just for higher payment, but also for a cut of the new markets for media distribution. There have been a ton of technological advancements since they last determined their contract that have opened up new revenue sources for the studios. Let's give an example: iTunes. From what I can gather, these writers (for such successful shows as 24, Lost, etc.) haven't been getting an appropriate cut (if any at all) from tv shows being sold on the internet. There were other sources that weren't specifically mentioned, but the point isn't how many sources are opening up; their contract needs to include all possible revenue sources. This blog is definitely biased towards the writers (mostly because I fancy myself one), but whether I was an actor, writer, or whoever--if I put my effort into a creative endeavor/project and someone else was making money off of it (even if they deserved to because they had put the initial money into it), and not sharing those profits, well... it's strike time.
I'll keep up with this as much as I can and let you know more as I come to understand it better.