Many projects, you could write an initial version in Ruby, Python, Java or whatever, and you're mostly going to be ok, at least while you explore the product/market fit. Maybe you'll have to redo some of it later, but that's likely anyway, so the best approach is to use something that can do a lot of different things reasonably well, and lets you develop quickly.
Erlang always feels to me like it is the best in the world at a few things, and not so good at all for others, meaning it's a bit more dangerous: veer out of its sweet spot, and you're probably better off switching to something else.
I also think that Erlang is more along the lines of Smalltalk or Lisp: pioneered some great ideas, but someone's likely to take them and do them in a more palatable format for the masses. Go and Scala, for example seem to borrow some concurrency ideas from Erlang. Node.js is also a "worse is better" competitor which has a huge advantage in terms of the language it uses (Javascript is orders of magnitude more common than Erlang), even if the actual code written for it is not nearly as elegant as Erlang.
Many projects, you could write an initial version in Ruby, Python, Java or whatever, and you're mostly going to be ok, at least while you explore the product/market fit. Maybe you'll have to redo some of it later, but that's likely anyway, so the best approach is to use something that can do a lot of different things reasonably well, and lets you develop quickly.
Erlang always feels to me like it is the best in the world at a few things, and not so good at all for others, meaning it's a bit more dangerous: veer out of its sweet spot, and you're probably better off switching to something else.
Here's something I wrote about it a while back:
http://journal.dedasys.com/2007/09/22/erlang
I also think that Erlang is more along the lines of Smalltalk or Lisp: pioneered some great ideas, but someone's likely to take them and do them in a more palatable format for the masses. Go and Scala, for example seem to borrow some concurrency ideas from Erlang. Node.js is also a "worse is better" competitor which has a huge advantage in terms of the language it uses (Javascript is orders of magnitude more common than Erlang), even if the actual code written for it is not nearly as elegant as Erlang.