As far as I can tell, they are a bit less worried about following "rules". On this board there are no quilt police, which is awesome, but in real life the guilds are likely to have a fair amount.
Also, a lot of the contact is done online, while most quilt guilds have no online presence at all. In my area there a local guild that if quite large (I believe they have hundreds of members) and they don't have any sort of online page at all.
I kind of agree that "modern" quilting is all in the eye of the beholder. I have books with antique or vintage quilts that look really similar to what some people call "modern". I get a little confused when people talk about it, too. It seems to mean something different to each person. Which is fine.
The new quilt guilds seem to attract young women who are mostly drawn to the non-traditional. From what I have seen posted on blogs there are show and tell times where a lot of original work is shown. I can see this "movement" creating individual free thinkers, which is pretty cool, whether or not people are reinventing the wheel. They are still thinking and sewing and quilting. Pretty awesome no matter how you look at it.