This does however rely on the potential of elgg servers on seperate machines being able to "link" to allow the perusal of common groups and view user profiles.

Are you wanting to have multiple Elgg instances running, and to have them act like a single instance? Or are you wanting to allow users to migrate between instances transparently?

It will also probably rely on the ability of Elgg to run on an SSL connection.

This is server-level configuration that is independent of Elgg.

Syncing data between sites (federating), is not something we support. I've wanted to for a long time but just never had a strong use-case. You may have one here.

Elgg works fine over SSL. You just have to set it up on your server and then set the URL of your Elgg instance to "https://..."

Ah, brilliant, I'd been wanting to know exactly what to call it, federating, yes, I could see it being the only way our customers would allow their employee's to discuss our software.

Ok, no problem, I'm glad I'm not the only one who thinks it would be a good idea though!  Diaspora does it I believe, however that doesn't run in anything like the environment of our software as far as I can see.

Many thanks for your reply Evan,

Andrew