how to count nfs clients attached to my server?

[Skunk Worx]

Is there a way, on a server, to discover how many clients are currently 
attached to a NFS file share?

I'd like to be able to see a list of the clients that have "my" NFS 
share mounted.

It's my understanding /usr/sbin/exportfs gives a list but it is not 
reliable as it depends on clients un-mounting the share properly.

I suppose the nature of NFS makes it impossible to maintain/calculate an 
accurate client list, but I thought I'd ask anyway.

---
John