They could also call out the flip side though, right? Dropbox could negotiate deals with the ISPs to "box out" smaller competitors. Maybe it costs them upfront but it also solidifies them in the market.
Yes, if you're a short sighted MBA that wants to encourage your own extortion
This is the problem of the tenant, the renter. The landlord can change the terms and eat into your profits. At some point it's not worth dealing with them, but it's not always easy to leave.
If you're Amazon (Dropbox), you have a strong position to negotiate better shipping (network) rates from FedEx and UPS (ISPs).