disclaimer I'm a Job hopper ;)
EDIT: You mention specifically start-ups. Ok. There, however, there is reward presumably commensurate with the risk a participant takes. Also, the work is probably more challenging and interesting. I hold that neither particularly apply to other sectors, speaking generally.
If you're looking only for people who can put themselves in that position, then I'd bet you'd find a good number of them to be job-hoppers.