The word ratepayers is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 15
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (22 words)
aerates, praters, prayers, reapers, reparse, repaste, repeats, reprays, rerapes, respray, restrap, retapes, retears, retraps, retypes, satrapy, serrate, spearer, sprayer, strayer, taperer, tearers