"From what I heard, there were 14 teams on the original cast:

Joe & Bill
Frank & Marge - Didn't wanna go. Were replaced by Uchenna & Joyce, what was terrible, since they already won.
Kevin & Drew
Ozzy & Danny
Flo & Drew - Flo said she only would race with Zach, were replaced by Eric & Daniella
Kelly & Jon - Quited going, were replaced by Dave & Mary, what was really terrible and didn't made any sense.
Charla & Mirna
Colin & Christie - Christie was pregnant, they were replaced by John & Voti & Jill, what was freaking terrible, since CC are great racers and characters, while JVJ are average racers and almost unexistent.
Kris & Jon - Cut
Rob & Amber
Meredith & Gretchen - He had to do a heart operation, replaced by Teri & Ian
Linda & Rolly - Rolly wans't old enough. Were replaced by Marion & DJ, who quit on the last minute.
Dave & Lori - Last minute cut
Dustin & Kandice"