When we profiled UK startup Failbetter Games in May, it was in part because the company exemplified Fred Wilson's call to build "killer apps" using the Twitter platform. (That, and their award-winning browser-based game Echo Bazaar is pretty darn fun.)

Yesterday, Failbetter Games announced via its blog that "Echo Bazaar is coming to Facebook around the end of July." And chaos ensued.

OK, not chaos, but certainly a fairly angry response from a small number of the game's players, many of whom said they played Echo Bazaar because it wasn't a Facebook game. They were "horrified." "Incensed." "Dismayed." "Angered." Many players invoked the privacy concerns associated with Facebook. Others pointed out the "spam" that Facebook social games can cause.

Alexis Kennedy, the "Chief Narrative Officer" of Failbetter Games, addressed the concerns one-by-one in comments on the post and clarified: the game is simply adding Facebook Connect as an authentication method for the game. Players will not be forced to add their Facebook information. The game will remain browser-based.

With the problems Twitter has experienced over the last month of so, the startup's decision to add another authentication method is not surprising. When Twitter is down, you cannot play Echo Bazaar. Plans for a Facebook expansion have been in the work for some time, says Kennedy, as the company knows it's been missing out on potential players who don't have and don't want Twitter accounts. Kennedy adds, "the outages last month were quite alarming and pushed the plans forward by several weeks. When every outage cuts off your revenue for the duration, dear me it focuses your attention. If the majority of our users auth via both services, we're covered against outages unless both suffer simultaneously."

Players' response to the addition of Facebook Connect surprised Kennedy, and as one commenter noted, "Good GRAVY, you would think the EB team just burned an orphanage!"

There are pros and cons for building your startup on other people's platforms. And there are certainly pros and cons to each of the platforms you might choose, as well. Failbetter Games' experiences navigating its users' concerns with one platform, another platform's continued instability, and the desire to expand its player-base demonstrate just a few of the complexities.