For play-by-play data and game statistics, I see several uses:
a) Feed a play-by-play flash interface the so players can watch the game (in abstract) from the sportsbook site. For this, the data quality and timeliness is not critical.
b) Create a statistical database from which create good lines on props. Live is no longer a factor here, and historical is.
c) Automatically create and grade props on common game statistics (how many strike outs, fly outs, missed field goals, etc).
d) Data to assist line manager for live lines or spread betting, especially if the time delay is significantly less than cable.
e) Live wagering on game events in above mentioned interface. For example, next pitch: strike, ball, or hit. For this, the feed must be faster than broadcast/cable television and must correct mistakes (something definitely not true of the feed Yahoo uses).