First of all, I'm sorry for reacting so late to your original reply - I'm not quite used to the forum yet and the notifications were going to places I don't dare check too often :).
The size limit is precisely one of the things I had in mind when talking about SLAs. Thanks for the info! The limit of 100Mb is for a single file or for all of them (if the former, what is the total storage limit per organization).
As regards other SLA-related things, I'd be interested in knowing whether the below is either in place or possible to implement. I'm of course aware that such things would require investments on your side and perhaps it could be . Also, the below is kind of an ideal scenario and datahub is a great and most usable service as is :).
Retention of the data: If uploaded, can you guarantee that the data will be available for a certain period of time?
Notification on end of data retention: If for some reason you won't be able to host the data, will there be a time period (how long) for which the organization can make a copy of the data before it becomes inaccessible?
Availability of Service: Are you able to guarantee a percentage of uptime? If there's a disruption of service, can you commit to # of hours the disruption will be removed/mitigated?
API limits: Are there any limits specified on number of calls a user/member of a registered organization can make?
Last but not least, do you have something like a public backlog of the features you're working on and where you could use outside help? I'm thinking that it could be a good way for municipalities (or other gov agencies) to participate on the cost and basically give something back for the great services they're consuming. Not sure it'd work, just an idea :).