I think noting that grappling is not based on feature size would be nice. It is something that will come up.
Looking back at the feat, snatch bases itself on improved grab (At least the version used by D&D hypertext, which I hope is the most recent). Which, by default, only works on creatures up to one size category below your own.
However, improved snatch from draconomicon is worded as though snatch had no effect creatures larger than 3 size categories below you. This could cause some confusion.