Maybe you can scan email coming into your corporate accounts, looking for LinkedIn SMTP servers in the headers? It may then be straightforward to find out (after the fact) if your users are using this service.
Aside: as Raymond Chen often asks, "What if two companies did this?" Can you layer this service with a hypothetical similar one from Facebook? If not, it seems like a huge first-mover advantage.
Right, first mover. I'm afraid LinkedIn has selfishly crossed a line that we will all suffer for. Other companies will no doubt try to do similarly idiotic things in the name of "convenience", "features", etc.
Aside: as Raymond Chen often asks, "What if two companies did this?" Can you layer this service with a hypothetical similar one from Facebook? If not, it seems like a huge first-mover advantage.