The costs. Tens of thousands for flights / hotel rooms / booth rental only to advertise to the hundred or so people who show up, most being from other coins.
That, in bold.
In order to get NEM to have a wider adoption outside of those already familiar with crypto's, things like youtube and facebook would be my first port of call.
I completely agree with this point. IMO Bitcoin would have reached way more people by now if the marketing stopped focusing on the tech side, and focused much more on the usability side.
A lot of people are happy letting banks hold onto their money simply because it's the most convenient option for them, once a crypto is proven to be as convenient as online banking, I think we will see a huge adoption rate (honestly there is no reason that it shouldn't be way more convenient than online banking, there's no BS signup and verification process with NEM).
Actually, i think the rationale behind alot of the "average joe" user goes a bit like this:
1. They read FUD in mainstream media which in often cases only reports on stories that are controversial or negative (on the subject of crypto's that is) - negativity is frequently good clickbait as people are more inclined to express outrage or negativity then they are praise. It's a human trait. (Although granted, Bitcoin deserves criticism in many respects, if it didn't, i wouldn't invest in non-PoW coins, however mainstream media tends to literally spread FUD when it deals with Cryptocurrency, largely through ignorance and a agenda, this leads to outright scorn, not criticism. )
2. The corresponding opinion as a result of mainstream media makes them uninterested or inclined to believe Crypto's are scams or unsafe - and in many respects, they're right. This forum is full to the brim of scamcoins. Even bitcoin, being still rather young, is volatile in terms of valuation -this makes it unsafe to stash away your hard earned savings/money in it.
With the above things in mind, NEM will likely struggle to make it into mainstream adoption unless it's able to market itself like Bitcoin did; on the allure of "money for nothing" or "mining". I for one think a few viral video's and some well placed, timed Facebook marketing is in order - but obviously on more honest and transparent principles.
The biggest thing going for NEM right now is it's rather large initial distribution - this gives it more security, and the more who already join in, the more secure it will become.