Who else is attending a conference that you are attending?

Conferences often publish a list of companies attending their conferences. This is partly done to promote the conference ("If Raytheon is here, you should be here also!"). But it also helps the attendees figure out who else will be there. As the Association of Proposal Management Professionals noted in its attendee list for Bid & Proposal Con 2013:

Some of these companies are your competitors, some are your partners and all of them are coming together to learn real-life, take-away trips, trends and techniques to help them become a better proposal professionals and lead their company to more wins.

While it's interesting to see the names of companies who are attending, sometimes that doesn't tell you that much. The aforementioned Raytheon is sending people to this conference. But even though Raytheon registrants used three different company names (Raytheon - Integrated Defense Systems; Raytheon Company; Raytheon Missile Systems), that still doesn't tell you a lot about who will be there.