Does my company need to be on Twitter?

My small-ish company (travel industry) is considering getting started on Twitter, but they are unsure exactly how it could help them. We are on Facebook, but that’s because everyone is on Facebook – my research showed that the Twitter audience was almost 10x smaller.

Obviously, we could keep current and prospective customers updated by tweeting the latest deals and all (that is, IF they are even on Twitter) but…what else would we do? And why would we do it?

Why is Twitter important for businesses?