I can think of a bunch of reasons, none of which are particularly compelling either way.
Reasons not to delete member accounts:
- There may be other things people do, like have notification set up for old threads on issues that they want to keep an eye on (e-mail notifications, etc)
- They may be registered here so that other people can contact them for clan or other reasons, even if they don't log in or post often (e-mail notifications, etc)
- The amount of space used up in the database used for these inactive members is under 1MB. By comparison, the entire forums SQL database is 350MB, and the attachments and other forum files take up 2.5GB. The server has over 100 GB free still.
- There would be no performance increase from removing these members
- The headache of me dealing with anywhere from 1-2000 e-mails from these deleted members about "why can't I login?" is not worth it at all, considering I haven't found a single real benefit of deleting these members yet.