I'll admit it bothers me when authors only have Kindle books, but not because I don't want to buy the Kindle version -- I want to leap in and tell them about all the other stores where they are missing out on sales!! I worry for indie authors, what can I say?
I can understand it, though -- it's not easy to publish in multiple format. I'm writing in Word and hand-converting to epub, and am somewhat concerned about the mobi conversion process down the line. *sigh*