.mobi domains are whitelisted by network level transcoders
Designing great mobile sites takes time and effort to get the most out of the limited screen resolution and navigation mechanisms of mobile phones. Having invested money and time in creating your mobile presence, you don't want a third-party transcoder modifying your site ... but this is exactly what happens when you use a non-standard name for your mobile Web site. As a rule, .mobi sites are automatically whitelisted by all network-level transcoders, so you can be sure your site will render as you intended on all mobile devices.
.mobi domains offer better search engine performance
In North America alone, search engine marketing last year was at $12.2 billion and is forecast to grow to $25 billion by 2011. Those numbers show that search engine performance has become crucial to the success of any business. Because every .mobi domain registered gets its own entry in the Internet Zone File -- the files that search engines use to start their crawls -- your site will automatically perform better than any other naming convention. Additionally, search engines detect when searches are being made from mobile devices and prioritize their results accordingly. Because .mobi sites are high quality and made for mobile, they are automatically brought to the top of the mobile search results.
http://mtld.mobi/resource/top-5-reasons-why-you-need-a-mobi-name