Box does have "network effects," even if they're not as strong as Facebook's or AirBnB's, because once you get thousands of employees at a company using your product, it's hard to tear that out and replace it with a competitor's product.
The platform strategy makes a lot of sense, because that's how you can turn weak product inertia like they have now into strong product inertia: once you have a big ecosystem spring up around your product, you have Microsoft-level staying power. I don't know how realistic that outcome actually is for Box in particular, though.
That's not what "network effects" means, though. Facebook and AirBnB presumably get better when more people join; their products are better with more users than with fewer users.
It's easy to see why having your entire company using the same service is useful. But it's hard to see why "having more users" makes Box a better experience for its other users. Is Box better at a 5000 person company than a 10 person company? Or when 1000 companies use it vs. 10 companies? If not, it's not benefiting from network effects.
Is it a network effect if it's only within a company? For example, because there isn't any (good) data model that allows for resource reservations, calendar systems within a company are always on the same platform so there aren't conflicts in booking meeting rooms (which, even when calendar programs were on the same platform, was a big problem from around 1995-2000). But that doesn't mean people outside the company can't use a different calendar program and send .ics invitations.
Right, I think the GP described a way that they might have "staying power" and be entrenched within their customer organizations, similar to how a poster described that Square might have that same quality.
I wouldn't call what you describe a network effect - it's a classic switching cost/lockin, but not a network effect.
A company with 5000 Box users is a single paying customer with zero network effect. It would be a network effect if there was some significant benefit for other companies (other potential customers) to start using Box (and not something else) in order to cooperate, but I'm not seeing that much.
The platform strategy makes a lot of sense, because that's how you can turn weak product inertia like they have now into strong product inertia: once you have a big ecosystem spring up around your product, you have Microsoft-level staying power. I don't know how realistic that outcome actually is for Box in particular, though.