I still haven't taken a dip in .mobi, and with all the "premium"d names that will be auctioned off, I may never dip into until it gets big. What irks me is when people who are heavily into .mobi talk down to people that aren't as if they are enlightened and those who aren't getting .mobi names are not. The same thing goes on with IDNs and it's repulsive. My opinion is that we're all out to make money, so let's do it and enjoy ourselves. Some people treat particular markets like it's their religion!
That said, while I'm not into .mobi yet and wasn't impressed at all with Pinky's presentation at DomainFest on it, I wouldn't be surprised if .mobi works out. A lot of people treat .mobi much the same as decent ccTLDs like .in, .cc, etc. and have the whole ".com is king, everything else is crap" opinion about it. All I have to say about that is I've made pretty good money from scratch largely due to ccTLD names, and I'm sure some people will do the same with .mobi. Everyone has to start somewhere, and the advice I would give to .mobi registrants new to domaining is the same I'd give to ANYONE starting out: research any and every name you get and be extremely selective. Most of us that have done this for a few years have a knack for generally knowing what's valuable and what's not acheived from our experiences in the industry, and those new in the industry have a tendency to register anything that looks good, not realizing that they are not their market and selling domains, especially newly registered names, is never easy.
As for age, I can't believe anyone would bring up "so-and-so is X years old, so ignore what they say" or anything of the sort. I'm only 24, have been speculating since I was 21, and have been aware of the industry and following it since I was 17. While I've not had any sales beyond $2,000 yet (which would leave some idiots to think I'm not successful), I'm staring at least one mid $xx,xxx sale in the face come Traffic auction time (hopefully 3 or 4 if I'm lucky!), make $2k/month in PPC, and have built up a portfolio of names that has gotten compliments from all sorts of people. I was glad to get as much respect as anyone else at DomainFest despite probably being one of the youngest ones there, and I frankly detest any talk that one's youth may inhibit their domaining abilities.
Even if GT is being negative about .mobi and you like .mobi, so what? He's a critic of the extension and you're convinced you're going to be making a lot of money...why even let it bother you? I laugh all the way to the bank at anyone detesting ccTLDs...they probably have their own market, but they're missing out on mine!