Not sure I quite agree with the premise (for e-mail at least)
Specifically: "There aren’t many business that don’t need archives of their files and emails that their employees can reach with ease."
Having every e-mail ever sent by every employee you've ever had on file permanently is excessive, expensive and at the end of the day a serious financial liability. The reason that it's a liability is that if you've ever been involved with a legal discovery exercise, the volume of discoverable data will directly impact the hours your legal counsel has to dig through, and consequently how big your bill is.
This is not to say that archive (from a storage extension standpoint - not its other use for compliance journaling) is unnecessary.... just that given the choice there are *many* users who would keep everything, indefinitely, and if that is not critical for your business that they be able to do so, you would be well served by not allowing infinitely expandable storage.
1.) Understand your legal requirements - this is your baseline
2.) Understand your business requirements - this could mean multiple retention/usage profiles above and beyond baseline legal requirements
3.) Implement retention policies (ex: call center employees can only keep mail that is less than 1 year old, etc) that align with your legal and business requirements
4.) As necessary, provide adequate capacity (either native to your messaging environment, or by extending through a secondary archive system) for users to keep data within their prescribed retention profile
5.) Restrict the use of local archives where possible (i.e. GPOs to keep Outlook from being able to create/use local .PSTs)
In essence, if you need it... keep it on the server or server + archive extension. If you don't need it, get rid of it!