I impose a 300MB limit and adjust upwards for those who have a really compelling and logical reason for requiring more PERSONAL space (you can read that as; I don't adjust upward for personal space). Even 300MB is overly gracious considering that this space I'm allocating is for PERSONAL use. I am responsible for maintaining corporate resources, my budget does not cover an employees' non-work related activities and our HR department appreciates the fact that we have little or no personal data to police.
If a user requires additional storage space for work related data then they are provisioned Departmental or Project directories which have substantial space but they do have limits imposed until such time and requirement necessitates a change of that limitation.
Effective Data space provisioning is important for several reasons. If a lack of restriction exists, an exuberant data storer can significantly change a backup time window or even fail a backup session altogether. Further, storage space can be expensive or additional infrastructure has to be built in to accomodate certain thresholds of disaster recovery, raw storage space or server performance.
Whether your Admin refers to his allocation as NAS, DASDI, ISD or another form thereof doesn't really matter; nor is it an indication of whether he/she's a throw back from the 80's. My point being; that he knows what he's talking about and he could refer to the resource as WCM (Wild Crazy Mushrooms) and it won't make an iota of difference in understanding to most end users. All you need to know is that you have space restrictions, if you need more than you or manager or department head has to authorize the change and it has to meet compliance standards in place.
Enjoy your 500MB of PERSONAL space. I wouldn't give you that much.
I actually like brtspears2's policy in that personal storage space is not allowed.