Changing Jobs Often Hurts Chances?

I'm a 26 Y/O white male with good-but-not-great stats (3.4 GPA, 760 GMAT). Since graduating college, i've spent roughly 1.5 years at 3 jobs. I've worked at the leading IT research company, leading EMR vendor (the EMR of Stanford, UChicago, Northwestern, and many other leading institutions), plus a h...