It's no worse than someone throwing an actual frag grenade, yelling grenade, and it's a dud. Not to name names but there are people who's grenades either always go off prematurely or take about 15 minutes to detonate.
Anyway, if a grenade is tossed into a room, impact or timer, and it goes off as it should, you're probably dead anyway. Trying to get out or away knowing someone is outside or around the corner waiting for you seems kind of silly. Properly deployed grenades should involve planning the choke points and a firing line. Either you come out dead or will be very soon!