Sure Quinn, They are trying to create a need that does not exist. Sites can be optimized to appear properly on mobile devices without the use of another ext. There is no need, just the desire to market another domain product, an ugly and awkward product at that. People can just as easily type .com into a mobile device (and would be more inclined to) than .mobi
Question - if it's a domain name from mobile devices (ie phones), then why a) make the domain name longer and b) use characters from the same key, which means you have to wait the 3 seconds until your phone lets you start the "o"?
All .mobi sites will have to display at lower resolutions, at the moment often what happens is the phone downloads all the extra stuff and throws it away, which is expensive when users are paying by data volume.
Whether .mobi is implicit or not, users will know that all .mobi sites will work well with their phones.
If the browsers on phones do default to .mobi (as browsers on desktops sometimes default to .com) this will give .mobi instant typeins as well.