Going by way of Kleenexes and Band-Aids, the iPad has become the word people use when what they really want to say is "tablet." The Associated Press has a whimsical report on how Apple is changing the English language, and the "genericization" of the word "iPad"--or in less jargony terms, the point when a product has become so ubiquitous, it becomes generic. A lot of their information seems to be anecdotal, since the AP doesn't cite any studies of how many people use iPad unintentionally (they do talk to linguists and marketing analysts), but if you think about it, it'd be hard to really ask that question in real life ("What do you call this computer-like object that you can touch?) without giving away the real answer.
The iPad's ubiquity is also Apple's latest last laugh, especially when compared to the jokes made about the name when the product first came out. But it isn't all fun and games when it comes to being the best known brand. The AP warns about the pitfalls of genericization--that genericization could dissolve trademark rights (which we don't think is the case when it comes to Apple and its very active legal team) or that it could sully the appeal of the iPad and make it a downmarket term (more likely we guess?). "It's like if people start calling station wagons Bentleys." writes the AP "It can diminish a brand's reputation."
Though, we don't think being downmarket be a problem with Apple, whose financials have them poised to be the U.S.'s first $1 trillion company or its $829 iPads. And, as the AP reports, there are plenty of companies who are fine with genericization. Just ask Google.