"Blackboard, Inc. is currently the heavyweight of the course
management software field. The software is closed by nature, which
is certainly limiting for many schools, but most likely isn't the
reason Blackboard's grip on the market is slipping. According to
The Chronicle, it has much to do with the software's inflexibility
when it comes to connecting with related course sites made with
open source applications, and even more to do with Blackboard's
disquieting lack of customer support."