Many domainers don't see use for the TLD, I don't either.
I guess some top-level domains are good for it, like Ringtones.MOBI, but then you have to consider the fact that ordinary people are exposed to .com, .net, .org, and country code domains more than anything else - meaning - I doubt if someone saw "ringtones.mobi" on a television comercial they'd know what it is.