i'll start:
#1: Sharapova. Especially with betting on under/over games, shes horrible.
2: Radwanska: same as above, she randomly DESTROYS 10 ten players, then starts losing sets to people ranked 100 sports below her.i'd recommend never trusting her for over/unders.And the thing i've noticed is that the most popular over/under, her games seem to always go the OPPOSITE of exactly what most of the public are putting their money on.
2 other people who have been frustrating:
.Virginia Rizzano or whatever her name is. Just completely gives up at times and seems to just lose games on purpose.
Phillip Petzchner: this guy recently had a handicap of +3.5 against an out of shape Roddick that got destroyed by Denis Istomin.He was doing fine until the last set and then just pretty much gives it up 6-1