Consistency can be an issue, languages which break from standards, or even what you're used to can be difficult. I grew up on C/C++, and it was the first real

Consistency can be an issue, languages which break from standards, or even what you're used to can be difficult. I grew up on C/C++, and it was the first real language I learned, so anything in that realm (Java, PHP, Perl, etc) is like riding a bike. For that same reason, Ruby was kinda hard to grok for me. But I think documentation (books, available source code, tutorials) is the biggest issue. Finding a practical PHP or Ruby tutorial is way easier than a Scala or LISP one. I'm the kind of person who learns by reading other people's code, so I've never been interested in the more obscure languages because of that.