Site collections, or sub-sites, in SharePoint Online?

Question

We have an established SharePoint 2010 intranet portal, which has many and various team sub-sites.  These sub-sites are created on request - sometimes it's because one of our locations wants their own little area to share documents, or it might be for
a company-wide project or initiative.
We are now slowly moving over to SharePoint Online.  Mainly, it's to replace Box and Dropbox (which some teams use), and allow our staff to share files externally if needed.  Nothing special, just a document library.  More often than not,
each site will have its own unique permissions.
Now, our SharePoint 2010 site is one large site collection (wasn't my idea).  As an administrator, that makes my life quite easy as it's one content database, one set of content types, etc.  But, with SharePoint Online, I don't need to think about
content databases, and won't be using custom content types with these sites.
So, I'm a bit stuck.  My options, as I see it, are:
One large site collection (pretty much a no-go as these shared files might get quite large)
One site collection for each request, no questions asked (which might lead to hundreds of site collections)
Create a site collection for each office location, and then a sub-site for each team in that location (as requested) - and also create a site collection for each company-wide function, and create a sub-site for each project within that function
Can anyone give any pointers towards the "best" option to use here?

Answer 1

it always depends on different things. 
One of the key elements I always use to decide site vs site collection is security boundary.
If the target site has a high level of confidentional information, I prefer a dedicated Site collection.
If it is just a smaller team (or broader team) to share info with you can easy use sub sites.
Looking at the boundary & limits is also wise to do. (like the 5000 item treshold in a view on a document library)
A document library should in practice not really be used for multiple teams, however it is possible. A lot of dl's within a site is also not that intuitive for a lot of end-users.
A office location can be use, however, a lot of work is done across office locations. (now or in the future)
One site collection per each request is not by definition a bad thiing... however please be in control (governance) of the owners. For example let a site collection owner every x months acknowledge that he/she still needs that site collection or that it
can be removed.
One Large site collection is asking for trouble in the end. however for a publishing intranet only it can be good.
Good luck with your choice for your environment!
You can also contact me if you want to discuss more on this topic.
Michiel Hamers www.SharePointman.nl Don't hesitate to contact me for a SharePoint/O365 question.