Understanding Dynamics CRM “Activity Parties”

Many of the entities in Dynamics CRM are hard to miss: Account, Contact, Opportunity, Case and so forth are all front and center, exposed in the Site Map and Advanced Find and other places. Some are harder to find but still important to know about. “Activity Parties” are in the latter category: a little too well-hidden, but useful nevertheless!
 
The Activity Party entity serves as the “intersection” entity in the many-to-many relationships CRM has between certain Activity entities and the front-and-center ones I mentioned above. For example, look at the Service Activity form and you’ll see a “Customers” field, which if you click on the lookup you’ll see you can select multiple Account or Contact records. Compare this to the standard “Regarding” field, which only lets you select a single value.
 
It’s one thing to select multiple customer records and associate them with a service activity (seminar, training class, user group meeting, soccer game…) but it’s another to do some nice reporting on that afterwards. How can you use Advanced Find or the Report Wizard to see which of your customers attended which events?

Here’s a YouTube video I recorded that demonstrates this using the Service Activity entity. Let me know what you think…and if you know of any way to get better video quality within the constraints imposed by YouTube, please let me know!