There's an impression that RoR is the language of choice for hackers because so many web-apps are built by it.
Web consulting firms use Java all the time because it's a proven technology with tons of flexibility. In RoR, the moment you step outside of the conventional MVC model; you are pretty much hosed, you have to write from scratch a lot of stuff that folks in Java have already enterprise platforms for. Specifically, if you want to do crazy data modeling with custom lazy-loading/cascading; or if you want to integrate some kind of high performance message system client-side; or have some kind of custom encoding/decoding of data objects from server-side to client-side (e.g., Rails to Flex/Silverlight). You pretty much have to rip up the whole rails framework.
RoR/Python is programmer's proverbial hipsterism to show how hip you are. But I would rather use Java when I need to deliver in actuality since you can't get laid anyways by impressing programmers.