They've been using conditional moves on gameknot for years, it can irritate opponents which is good in a psychological game like chess. Whenever I face a conditional move I always take my time to respond. If it's in the opening or if my move is obvious or forced, it's easier to dismiss, but if they've basically predicted a move that wasn't obvious, I'd be a bit worried and would definitely take more time than if they just made their move as normal, so in some cases it might work against you. You can alert your opponent to imminent danger.