Some great points being brought up and I agree there are definitely problems and challenges. However picking a remote DBA firm isn't like hiring an electrician or plumber for the day. It's something you enter into for the long term, with the idea you'd use the group regularly.

And for smaller environments, even if they don't know everything, they can provide some valuable peace of mind for a DBA going on vacation (for both the company and employee), especially if he/she's one of 3 or 4 in the IT department.