OK. Given your answer to the question (in comments) about the real issue from sysadmins POV, I'll sketch out the approach I use. It's a combination of clear policy and simple filesystem layout.
The policy: Each user "owns" his/her fileshare. IT doesn't own it; the user does. But like ownership of land within city limits, ownership comes with responsibilities. Clear directives are given as to what may and may not be stored in fileshares. So for example, work-related files may be stored in fileshares; personal music and movies may not be.
Conversely, every fileshare is owned by some specific person. This is important. If IT knows who "owns" what, then IT never has to make guesses about the business value of data found in "public" areas. We can merely go to the owner and say something like "Hey, you own this directory full of unknown data; please justify it in business terms or we will delete it."
Each fileshare comes with a quota (maximum size of directory) and that quota is initially set fairly low on purpose, say 200 MB. A fileshare's owner (and only its owner) may request increasement of the quota, but only with a business reason signed off on by the user's boss. IT may audit the directory for policy compliance before increasing quota. IT can look for seemingly unused data and ask owners to justify continued use of the disk space.
When a user leaves the company or changes jobs, his/her user directory, and any \Public or \Project folders, is 'inherited' by their direct supervisor, who is given a specific amount of time (say 14 days) to retrieve or redistribute any data found in that share, or find a new owner for it, before IT deletes it all.
Fileshare layout. Each user gets, by default, something like this example for a user named Bob:
\Users\Bob
\Users\Bob\Private (default permissions set so only Bob can read/write here)
\Users\Bob\Public (default permissions set so any employee can read/write here)
Bob has full control over permissions, and can create subfolders at need. If he wants to host project data, he can create \Users\Bob\Public\ProjectBlue and set permissions however he wants. With help from IT if he needs it.
At some point, ProjectBlue may outgrow Bob, and be moved to another hierarchy. Say \Public or \Projects or whatever. Which looks like this:
\Public\ProjectPurple (owner: Sam Spade)
\Public\NewEmployeeDocs (owner: current head of HR)
\Public\AdvertisingCampaigns (owner: Pat Seyjak)
... and so on.
I'd be very wary of running scripted cleanups through filesystems. IT's job is to keep data systems up and running well for business-related reasons, just like Facilities has the job of providing working desks to each employee. Facilities doesn't want employees keeping hamsters in desk drawers, but they don't go around cleaning people's desk drawers for them. Too many ways that can go awry. Imagine how you'd feel if, every month, Facilities went through your drawers and relocated anything they didn't understand to some basement storage locker, forcing you to go down there and reclaim it before they haul all unclaimed stuff to the dump.
We in IT do not know every facet of the business. If we assign ourselves the job of combing through all data and deciding which is business relevant versus which should be sequestered-and-or-deleted, we create many opportunities to make mistakes, interrupt workflows, and create antipathy between us and our users.
But we can create simple rules and organization hierarchies which push responsibility back to where it belongs: the employees closest to whichever facet of the business that generates the data.
Anyway, that's my (lengthy!) two cents. It may or may not apply to your situation.
A note: "owner" may be too strong a word. You may need to adjust that to fit company culture. Think "steward" or "assignee" or "principal".
Also, it can be helpful to have certain metrics. For instance, overall yearly capital and maintenance costs of storage are handy. If, for example, you're spending $400k/year on data storage (including equipment, power, backup, service contracts, administration time, etc), and Bob has somehow come to 'own' 22% of all in-use disk space, now you're able to discuss that usage with management, in concrete, understandable terms.
