Alex Williams has an excellent post about internationalizing a new web app as early as possible. Scrawlers is probably a prime candidate to internationalize right off the bat. There isn’t much static text on the site, anyway. Most of it is user-generated content. I’m willing to bet it isn’t as hard as I think it would be to internationalize.
The thought process is basically, “I have very limited time to put this app together. I don’t actually know if it will be successful. If it is, I can get to inernationalization later.” I think that’s OK, actually. I’m doing the same with many other things that would be easier up front: cookies vs DB hits, Rails ActiveRecord vs. tuned SQL, etc. Internationalization is one of many features that are pruned.
To me, it really is a matter of experience. If I were an internationalization ninja, of course I’d be including such features on day one. If I were a SQL master, naturally I’d drop out of ActiveRecord more often than not.
That being said, it is surprising to me that a company like 37signals would keep putting out new apps without addressing the issue. When their popularity started growing, it would seem an ideal time to build some internationalization-fu to leverage in their planned portfolio. Sucks to be them, I guess. :)