http://pittsburgh.craigslist.org/bik/1651245885.html
First of all, I would never buy a used helmet. Much less for a child. Second of all, this has been on clist off and on for over a year. Is it some sort of scam?
Hmm, a scam for $5? Seems unlikely. What's more likely is that the seller doesn't know much about cycling helmets (I'm guessing most non-cyclists don't), and figures it's okay to get a couple of bucks for something cluttering up their garage.
It's puzzling that it would be up there for more than a year, for sure. If I had a $5 item and it didn't sell, I'd move on.
I suspect you are not the average CL user 
On a side, but related note...You can get a free kids helmet at the Springdale bike safety program for kids which is sponsored by the Veterens of Foreign wars. I posted about it last year [http://bike-pgh.org/bbpress/topic/kids-bicycle-safety-program] with all the details. I think that it usually coincides with bike safety week.
New store in North Hills Village, Five Below, is a sort of up-scale dollar store. They have a bunch of new Bell-brand kids' helmets for $5. This is not a plug, but since it's on-topic and people (myself included) like to buy new, I thought I'd point it out.
someone should feign interest and see how low they can haggle them down... just to keep it off some childs head
