I dunno. It's a real business with real revenues, and tons of lock in. ORCL is worth $150B. It seems to me anyone who can steal marketshare from them could be worth at least 1% of that amount.
"This market is $XX billion, we only need to take 1% and we'll be rich" is a common startup fallacy. Stealing customers from Oracle is no easy endeavor.
That's very true, but Mongo has both a different product and dramatically different price point which should at least give them a fighting chance. You can't take on Oracle with a similar product that sells for 10% cheaper. With that statement, I'm really just parroting some of the tenets of the Blue Ocean strategy, but for the most part that book just makes sense and has validated what I've seen in competitive situations in the various industries I've worked in.
Oracle sold a product that was absolutely essential to pretty much every major business: there isn't really a good alternative to a transactional relational database running on middle-to-high-end hardware for a lot of companies. Selling something business-critical to customers with deep pockets is a pretty good business strategy. And they only had a couple of direct competitors in that space.