Cellphones can already browse .com sites. .mobi is just a brand; think of it as the .net version of the mobile web.
About 10 million Internet users in the U.S. use a PDA or cell phone to access the Internet. The number will certainly be growing as manufacturers develop new devices.
.mobi is not that 'hot' at the moment (being some none .com .net .org extension), but it can get 'hotter' in the future. Internet access via mobile devices has got great potential, people spend much time at airports, in traffic, lap-top is sometimes too big to carry around, mobile phone you can hold in your hand ('handy' is a popular name for mobile phone in Germany) and browse internet while walking down the street. I use mobile phone internet while I watch tv, eat, shower, play basketball or to check sports results in the middle of the night (it takes only about 3seconds and 3 clicks to turn on mobile phone and access internet, pc/laptop can't beat that).
Are you kidding? .mobi is overheated right now. It's dominating the global contender chart because of the Sedo auctions.
Sorry if I made wrong projection on its current state, I thought that having a .mobi domain will not make people with mobile phone internet rush to it because it's .mobi, at least it's not the effect it has on me at this time, and that site owners would still rather use .com(/wap) than short and direct .mobi as a forehand. Websites I visit via phone like ESPN, livescores.com and similar come with .coms, maybe they have .mobi but I oversaw them marketing it. I just checked that yahoo.mobi exists but I'm using its .com address via mobile phone, I never saw yahoo marketing its .mobi. I'm glad that .mobi is 'overheated' in the domain sales market.