What makes avant-garde avant-garde?

[MalignD at aol.com]

<< My fear is that over-commercialization of the art process and the 
co-optation of
potentially vanguard movements (especially in music) that very little is 
produced which could be regarded as revolutionary.   >>

It's difficult to see many in the forefront of art today (classical music 
perhaps excluded) who are co-opted.  Art is commerce and the artists traffic in 
it.  They aren't co-opted; they're entrepreneurs.  

And I think that your hope for art as a society-changing vanguard movement is 
touching, but hopelessly naive.  Those days are over, except, perhaps, via 
some unforeseeon commercial, eye-opening blockbuster, some artist co-opting 
commerce.  Possible, but not likely.