You're making two points, either or both of which may be good, but they are two different points. First, are they hard or easy? Second, are they distracting because they're fun/engaging? Either "problem" may lead to them being a huge time sink for startups and either may lead to them being perennially unfinished.<p>The good news is that a language for in-house use need not be finished to be useful. For example, FB's PHP compiler can't compile "eval." No problem, don't use eval in-house. If they were trying to "finish" it in the sense of writing a compiler for every possible PHP app, they would have to address that somehow. But instead, they punt on it and carry on using it in house.