MongoHQ has a licensing agreement with 10gen for the name. Plus, as already mentioned, MongoHQ works very closely with 10gen to not only promote the use of MongoDB, but to improve MongoDB as a database product.
I believe that the same could be said for MongoLab, a similar service.
I also believe that both services need to be certified by 10gen before rolling out new releases. Also, paying customers at a certain level have access to 10gen for support if the provider can't address the issue.
Long story short, both these companies have a good relationship with 10gen in the interest of growing the space.
