Don't forget RethinkDB, Mixpanel and Cloudera - those guys are solving some difficult, real world problems. Personally, I wouldn't classify massively distributed computation as a service boring. If anything, the scale (in numbers of users, amount of data) makes B2B of this kind even sexier than share-my-cat-at-my-location-agram.
There sure are boring things in B2B just as there are in B2C, but there are plenty of B2B business that are great fun and challenging as hell.