Plus it scales well and doesn't randomly lose data. Oh, and the project leaders are professionals who are honest and transparent about the capabilities of their product.

It scales, to a point. In my opinion however, any type of sharding/clustering is still a total mess in PostgreSQL. Most projects will however probably never need to.

How DARE you, sir, imply that we are not the next "Amazon"!

Kidding aside, I suspect with a little discipline, one could design a PG DB that could be ported to Oracle (Exadata???) should the need, and budget ($$$$$), for that sort of scaling arise. Cheap and safe now, Expensive and safe later (if needed)

Also, I seem to recall that PG scales up on multiprocessor hardware fairly well (vs say MySQL), so one can explore exhausting that limit first before more drastic measures are taken.

Shameless plug here, but my side-project (http://bedquiltdb.github.io) aims to provide a nice mongo-a-like programmatic API on top of PostgreSQL and JSONB.

In theory there's no reason why we shouldn't be able to support a nice transactions API in the client drivers too, I just haven't gotten around to it yet.