DEAR CRABBIT: agent touting on Twitter?

An interesting question has come from one of you.

Dear Crabbit
We hear all the time about how enormous agents’ slushpiles are. So am I right to view with suspicion an agent who uses Twitter to invite submissions, and/or one who is running a competition where the prize is representation? I don’t want my cynicism to stop me from pursuing a genuine opportunity but I’d hate to think I’m wasting