Why do merchants accept Bitcoin as valid currency? I suppose one could ask the same question about any form of currency, but I am curious how bitcoin became an accepted currency with no government backing it.
I think the best reasons right now are:


Marketing: being the first to do something attract a lot of interest and media.
No chargebacks: Bitcoins does not allow any kind of chargeback, which is not true for main payment systems (Paypal, Stripe, Credit Card).
Lower fees or no fees, just depends on how you use it.
Investment some people wants to hoard some BTCs and offering their services in BTC is the easiest way to get some.