well a complete stranger who's writing you on APC would totally understand if you said "i dont know you so I would feel weird writing a recommendation." But for people you know or met personally, I think its always great to help out.

Plus, if the guy you got hired ends up doing something stupid 1 or 2 years later, theres no chance they'll link it you or even remember your name. If you get 10 people hired and all 10 get in trouble, then wow thats tough luck and you might then have some explaining to do.