I've been intrigued with "modern quilting" and trying to define exactly what it is besides younger people who don't get particularly good vibes from quilting with older people. Melody Johnson suggested in a comment that MQ tends to involve a lot more white, fewer muddy repro fabrics and less fiddly piecing of tiny bits that have to match at the corners.
I have more clues for you today. Generation Q has a post about a block challenge in the Modern Quilt Guild, showing the four winning blocks from the Philadelphia chapter. I thought they were all excellent and they were certainly different from the blocks you would have gotten if your regular middle-aged-and-up quilt guild were to do the same activity.
The very existence of the challenge provides me with another piece of the definition of MQ. The rules were to use fabrics from a certain designer line. I have noticed that a lot of the MQ chatter has to do with designer fabric lines. I find this fascination understandable among new quilters, who may not trust themselves to pick out fabrics that will go together.
I do hope the newbies will outgrow designer lines as their own color and design sense matures, but acknowledge that choosing this particular design line for the challenge is a long step toward that goal. The collection is much more adventurous and challenging than the matchy-matchy design lines seen in so many shops and immortalized in so many quilts made by older ladies.
I note that the designer whose line was chosen for the challenge was a Project Runway winner; not sure that would happen so much in old-lady quilt guilds. I wonder how many young people have taken up sewing, whether garments or quilts, because of Project Runway! I don't watch it myself, because there's too much drama and too little actual sewing, but I think it's great that the show has given needle arts a shot in the arm.