We're open to it, should we find a certification process that actually amounts to anything.  Since our outset, we've been members of the National Association of Professional Petsitters , which entails a certain set of standards, and which offers a certification process in addition to that.
 

Unfortunately, that process involves little more than watching a DVD, and taking a written test, and forking over a few hundred bucks.  And (call us crazy, but...) that isn't the sort of thing we'd encourage anyone to take terribly seriously.  We might even call it a racket.  We may do it in the coming year, to rein in our liability premiums, but it's really not a substitute for understanding a particular animal's needs, and the environment in which that animal plays/lives.

 
If you know of credible certification programs, we're all ears.