I'm not sure I'd compare Snap with Twitter. Twitter has essentially flat-lined. Snap has only been monetized for a little over a year now and has at least demonstrated that they're capable of bringing in revenue, based on their ~$350M in 2016 and $1B 2017 projection. They're just beginning and I think they'll find more ways to capitalize on their large user base in the future.
I see your point - but when Twitter went public, they were still growing, and their valuation was lofty, based on expectations of considerably more growth.
Snapchat is in possibly a weaker situation: they are not making any money - and in order to justify their valuation, they really do have to grow for a long period of time.
I believe that Snap is 'similar to Twitter' in that Snap will not become like Facebook - i.e. 'ubiquitous and incumbent'.
I believe that Snap will likely 'hit a wall' in growth at some point.
The greater risk is that Snapchat may be a fad.
Twitter 'was a fad', but when the hype died down - they are still kind of a broadly usable tool for media, celebs - Tweets are used extensively in reporting coverage. This gives a lot of stickyness to the platform.
Snap ... is the 'zen cool' thing for 18-26 year olds ... but that could change very quickly. There's no reason that their user base can just switch to FB messenger (where everyone else is), SMS or whatever to do 'regular communication' when they are too old to be 'sharing irreverent stories'. And the 14-year-olds today, when they turn 18-ish may have some other cool thing to do.
So if we can separate the 'fad' and 'utility' parts of the platform - Facebook has a good deal of 'utility' that applies to a very broad base. Twitter has some 'utility' to a narrower base.
I'm weary that Snapchat just doesn't have the kind of 'utility' that it needs to survive after the 'fad' dies down.
That said, they have been good at innovating and 'staying cool'. A lot of brands manage to 'stay relatively cool'. They could adapt/evolve into something consistently cool, or consistently useful. Possibly. But there's nothing on the roadmap that says they would.
