But their ECM offering is basically Dropbox++ rather than Opentext/Hyland/Alfresco/etc. They don't have nearly the feature set of the big guys, and there aren't many enterprises particularly interested in ECM (the "M" part) who would take Box seriously. They might as a simple cloud storage platform, but only if they need something like that and haven't already got something similar from Google or Microsoft.

(I'm writing this as the person responsible for ECM & Google Apps at a large enterprise. We looked at Box and were non-plused.)