Most Helpful Guy
Only the ones that are just looking for sex (because you having feelings is an unwanted complication that they don't want to deal with) or the guys who never liked you in the first place.
Guys who are interested in you (for more than just casual sex) will appreciate your signs of interest in them).
Most Helpful Girl
Most of the time they don't. I would imagine they only lose interest if they get freaked out or realize they are actually not as interested as they thought they were.