I think it's tough hiring good Ruby/Rails people because they're all busy. And those that aren't, are probably not good to begin with...
(I think the OP mentioned "hasn't worked out as planned" with regards to hiring Rails talent, not erlang)
Then my statement was more directly referring to the Erlang piece of it.
One of the things that crosses my mind every time I start leaning towards one of the more exotic languages is whether or not I'll ever be able to find someone to maintain the software later.
Of course good PHPers are probably busy too.
I have never heard of a company scrapping a business deal because the world ran out of lawyers or accountants. The problem isn't a lack of developers, the problem is a lack of developers at the price the company is willing to pay.