According to the Forbes article "The Next Crisis to Avoid is in Student Loans," the concern is the high amount of student loan debt combined with a weak job market adds pressure to the economy. Specifically, this could be impacting first-time home buyers, as borrowers in their 30's have the highest average student loan debt balance at $28,500.
There's much more to the issue that is contained in the articles.
Here's the link to the "Grading Student Loans" post:
Here's the link to the article "The Next Crisis to Avoid is in Student Loans" from Forbes: http://finance.fortune.cnn.com/2012/03/06/student-loan-crisis/