I have been asked that question and have asked the question myself a couple of times. There are so many different technologies that I can choose to complement my current skill set, why Ruby?
Well, I came across an interview from EngineYard blog recently - Chicks That Rip: Ines Sombra.
Ines’ answer is almost exactly word for word of my own answer to the question:
What attracted me most to the Ruby on Rails community is how bold it is. This community is not afraid to experiment and innovate. What I find especially interesting is the prevalence of polyglot systems and cutting-edge data store solutions. Databases are put to the test in Ruby on Rails, and these applications are defining the future of how systems will be constructed. It’s amazing.
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The community, the rate of innovation and polyglot systems - this gets the geek in me excited.