So, call them "agility tokens". You've still got a limited supply when it comes to trying out new languages, new databases, new whatever. If you've got ten years Python and MySQL experience, and 95% of your codebase is in Python with data stored in MySQL, what do you gain and what do you lose by introducing Node.js and MongoDB into the mix? Sometimes it's worth the trade...other times it's not. But, Node.js and MongoDB is probably not going to provide enough of a productivity boost to make up for the costs of maintaining two codebases, two build/test/deploy environments, two databases, etc. You're making a trade; sometimes it's beneficial (usually long term), and often it's not (usually short term).
In short, yes, I'm buying this. I think it's a perfectly sensible analogy; a somewhat leaky abstraction, if you will, since none of us actually have any "tokens" that we are trading in for a new database. But, the meaning is clear to me, and I can't find fault in it.
> Sometimes it's worth the trade...other times it's not.
That's exactly what the article disputes - "It's not worth the trade if you had 3 of those already".
Sure, you could drown in meaningless (for your project) new technologies, and this is a risk you should be aware of. If that's the meaning of the article that you are referring to, I agree it is sane (and also wildly accepted). But that's not what the article actually says. What it says is that you get a superficial number of shots at new technologies, and that number is limited by time/growth.
In short, yes, I'm buying this. I think it's a perfectly sensible analogy; a somewhat leaky abstraction, if you will, since none of us actually have any "tokens" that we are trading in for a new database. But, the meaning is clear to me, and I can't find fault in it.