While not as common as with most styles of acoustic, capos are used by many of the top electric players. They're not a "cheater" — no one would question these players' ability — they're a stylistic tool.

The Edge (U2), Eric Clapton, Bruce Springsteen, Bonnie Raitt
Keith Richards, Tom Petty, Brian Setzer, Elvin Bishop
James Burton, Jerry Jeff Walker, Jimmie Vaughan, Dan Vickrey
Mark Knopfler, Pete Townshend, John Sebastian