First round picks immediately have a cap hold equal to the guaranteed money a player would get if selected at that position.
Such as, Jordan Hill's #8 pick, if acquired today, would have a 2.7M cap hold on it.
This is why if we traded for any first round picks at the deadline we wanted 2011 picks not 2010 picks. We got rid of Hill not just because he stinks, not just because Houston wanted a young player, but because his 2.7M was crippling our 2010 plans.
So I don't see any way we bother buying a 1st round 2010 pick.