Six teams, 169 roster spots filled as of March 31, 2008 (Opening Day for most of the league).
Obviously doesn't account for future add/drops; also doesn't include the "suck league" team that drafts later this week.
Team representation:
Arizona Diamondbacks: 11
Atlanta Braves: 11
Cleveland Indians: 10
Kansas City Royals: 10
Tampa Bay Devil Rays: 9
[...]
Seattle Mariners: 0 (purely unintentional)
4-time offender:
Conor Jackson (1B-ARI)
3-time offenders:
Adam Jones (OF-BAL)
Josh Bard (C-SD)
Kelly Johnson (2B-ATL)
Lastings Milledge (OF-WAS)
2-time offenders:
Adam Dunn (OF-CIN)
Andrew Miller (SP-FLA)
Asdrubal Cabrera (2B-CLE)
Billy Butler (1B-KC)
Brian McCann (C-ATL)
C.J. Wilson (RP-TEX)
Carlos Pena (1B-TB)
Chris B. Young (OF-ARI)
Daniel Cabrera (SP-BAL)
David Wright (3B-NYM)
Derrek Lee (1B-CHC)
Hiroki Kuroda (SP-LAD)
Huston Street (RP-OAK)
Jacoby Ellsbury (OF-BOS)
Jamie Moyer (SP-PHI)
Joakim Soria (RP-KC)
Jonathan Broxton (RP-LAD)
Justin Duchscherer (SP-OAK)
Justin Verlander (SP-DET)
Kosuke Fukudome (OF-CHC)
Matt Diaz (OF-ATL)
Peter Moylan (RP-ATL)
Rickie Weeks (2B-MIL)
Troy Percival (RP-TB)
Zack Greinke (SP-KC)