There is a certain portion of web pundits always banging on about this issue. Progressive enhancement is always the phrase used to beat devs over the head about their use of newfangled technologies.<p>The truth is, there is always going to be some subset of users/agents that won't be able to use your site. You won't reach everyone, not only for technical reasons but for cultural and linguistic reasons as well. Even if you make your stuff work in Opera Mini, who's to say the user on the other end reads one of the languages your site is available in.<p>The only thing left is to decide the tradeoff between how many of them, the experience itself, and the amount of work you will spend maximizing the other two. There is something about the web that makes a certain portion of people want to believe that tradeoff doesn't exist, and you're a jerk if your site doesn't work on everyone's toaster in Moldova.