Mobile World Congress ended a few days ago, and while there was plenty of news out of the conference concerning tablet devices running the open source Android mobile OS, there are also plenty of people who have already ceded the tablet market to Apple, based on the enormous early success of the iPad. They argue that Apple has a pre-existing ecosystem of applications and users familiar with iOS, creating huge barriers to entry. The thing is, though, that's what everyone said about the opportunity for Android on smartphones. They said that it arrived too late, and that Apple's iPhone would run away with the whole market. They were wrong, and many people are wrong about the opportunity for new tablets, too.