When it comes to infrastructure as a service, it appears to me that there is an imbalance between the sensitivity of information entrusted to external systems on one hand, and the standards such systems are held up to on the other.
EDIT: case in point, on http://mongohq.com I can't find a single mention of the word "security". The language is all about ease of use, performance, scalability, disaster recovery, and low cost, but as far as I can tell not a single word is spent on what procedures are in place to safeguard your data from unwanted access.
EDIT: removed inflammatory comment.
Like everything in software it's about tradeoffs. Maybe they erred a little too far on one side of the curve, so let's learn from that. But it's unfair to expect startups to be in the same league as banks security-wise. Do you have any idea how much a good pentest costs?
It's a great trade-off for most early-stage companies, because managing databases is hard. I'd rather leave it to the experts who specialize only in managing databases. You and your product team have a thousand and one other things to think about other than managing your database. Your provider may end up making mistakes, but that's part of the risk you take.
Security breaches are a mess for everyone involved, and we're in relatively new territory here in the Infrastructure As A Service space. Overall, I have little doubt that IAAS overall is a good thing. As an industry, we'll learn and improve on how to deal with all things "security", but we're clearly not there yet.
Also farming out a piece of infrastructure and having a secure stack doesn't have to be mutually exclusive.
Looks like the database is managed by MongoHQ. That's what OP is talking about.