I've never signed any agreement other than the usual disclaimer/waiver acknowledgement that there will be other dogs in the facility and sometimes things might happen between them.
I guess I'd find it a little peculiar to have an explicit contractual agreement for most of the classes I take. It wouldn't be off-putting, exactly, but I'd probably consider it pretty pointless.
ARCHMX TDCH Pongu the Insane, CD-C, RE, RL1X6, RL2X5, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, ITD (Akita mix, b. Jan 2011)