I was just looking at the N.L. rosters and I may have found the answer to why Choi slipped through waivers past the entire N.L. Right now, Choi looks like a decent backup first baseman or possible platoon partner with a right-handed first baseman but almost every team in the N.L. has a lefty starting or backup first basemen already on their roster. This is likely why no N.L. team claimed Choi.
N.L. East
Braves -- Adam LaRoche (lefty)
Phillies -- Ryan Howard (lefty)
Marlins -- Mike Jacobs (lefty)
Mets -- Carlos Delgado (lefty)
Nationals -- Nick Johnson (lefty)
N.L. Central
Cardinals -- Albert Pujols (righty) / Chris Duncan (lefty)
Astros -- Lance Berkman (switch) / Mike Lamb (lefty) / Jeff Bagwell (righty)
Brewers -- Prince Fielder (lefty)
Cubs -- Derrek Lee (righty) / John Mabry (lefty)
Reds -- Scott Hatteberg (lefty) / Adam Dunn (lefty)
Pirates -- Sean Casey (lefty)
N.L. West
Padres -- Ryan Klesko (lefty) / Adrian Gonzalez (lefty)
Diamondbacks -- Conor Jackson (righty) / Tony Clark (switch)
Giants -- Lance Niekro (righty) / Mark Sweeney (lefty)
Dodgers -- Nomar Garciaparra (righty) / Olmedo Saenz (righty)
Rockies -- Todd Helton (lefty)