So playing devil's advocate here, how can a guy get that girl to respond to him? What is witty, interesting and worth responding to?
Does he chase her until she responds? How many messages are too much? Where does it cross the line into harassment/blocking territory? A lady I worked with said her now DH sent her loads of messages until she "gave in". She said he wasn't his type but eventually responded, dated and they got married, etc. That's not my style, I'm more Eminem - "one shot, one opportunity..."
Also, if he is supposed to come up with something interesting and witty and he likes say 6 girls, spends 15 on each message before sending, that's 90 mins of his day spent sending messages which probably don't even get read let alone responded to. If he does this solidly for 1 week, that's 7 and 1/2 hours per week just for that.
If he is serious about finding someone, then it's either scatter gun or nothing. If he waits 2 days between messages before messaging another then he will be waiting a long time.
Unfortunately, IMO OLD is by design meant to be scatter gun. The site is called POF, and more people will try chucking out that net to gather as many fish as possible instead of spear fishing in the hope of catching "the one"! I've sent out "hey there" and received a handful of "hey there" from ladies too.
Did my efforts talking about "that guy" cover up that this is definitely not me?! 
You might want to watch this amusing take on OLD, it's not only men who cast their net out far:
www.ted.com/talks/amy_webb_how_i_hacked_online_dating
P.S - Where's a Hitch when you need him?