The Mozilla booth has been thronged with curious attendees all day. Carriers such as Telefonica are palpably excited about having another real open-source alternative to Android. Hell, the very orange Firefox knit hat -- with ears! -- might even be the chic geek accessory to have in chilly Barcelona. [Ed note: Maybe for those without a fashion sense to spare.]

The reasons why are easy to see: Carriers love free open-source operating systems because it helps to drive down the cost of the smartphone. This is particularly important as they look to sell cheap smartphones -- think $100 or less -- and seriously cheap data plans in countries where $200-plus devices just aren't an option.

In addition, some operators outside the U.S. aren't so keen on Google's Android strategy because Google stores emails that can be accessed on the Android phones on U.S.-based servers, which can cause regulatory issues. This has opened the door for an alternative such as Firefox.

The pure Web and HTML5-based nature of Firefox will also make it attractive to developers looking for the next cash cow after iOS.

Certainly, Firefox phones don't have to be an iPhone killer (or whatever bogus terminology is now in use) to succeed. They just have to work well enough, proliferate like Android and give many people a cheap and reliable way to get on the Web.

I can certainly think of some problems ahead. A smartphone that is someone's main connection to the world in many countries needs a good, reliable mobile payments and banking infrastructure.

From my limited research so far, I'm seeing some interesting apps but not everything I would think needed yet. I'm sure Mozilla and its supporters will move to address that.

Still, Firefox seems like the most interesting new contender we've seen in the mobile OS field for a while.

— Dan Jones, Site Editor, Light Reading Mobile