The principles of the modern quilt movement, as stated on their website, are these.
"Modern quilts and quilters:
- Make primarily functional rather than decorative quilts
- Use asymmetry in quilt design
- Rely less on repetition and on the interaction of quilt block motifs
- Contain reinterpreted traditional blocks
- Embrace simplicity and minimalism
- Utilize alternative block structures or lack of visible block structure
- Incorporate increased use of negative space
- Are inspired by modern art and architecture
- Frequently use improvisational piecing
- Contain bold colors, on trend color combinations and graphic prints
- Often use gray and white as neutrals
- Reflect an increased use of solid fabrics
- Focus on finishing quilts on home sewing machines"
They state that they are quilters first and modern quilters second, with their feet firmly planted in the "field of tradition". This style of design and quilting has been around for years and years, someone just slapped a new name on it and started promoting it as "modern". Like any style of quilting, or anything else for that matter, there is a huge diversity of ideas as to what is included within the label.
To reply to Holice's original question, because the 'modern' quilters are internet created, younger, and electronically 'with it', they seem to communicate primarily through blogs, Flickr and Facebook rather than 'old fashioned' message boards. More power to them if it brings new quilters to the fold, but I hope they don't get too wrapped up in segregating themselves from the foundations of the craft.
ETA: As far as using patterns, I totally disagree with the statement that modern quilters do not use them. There are a bazillion books and patterns available with the 'modern' label on them and I guarantee they're not all being purchased by traditional and art quilters. Many of the 'formerly known as' contemporary quilters (Denyse Schmidt, Ringle and Kerr, etc) have rebranded themselves as modern quilters just to appeal to this audience.