The Walker Cup is a match-up of teams from Europe and the USA, in a format similar to the Ryder Cup, but for amateurs only. Way back when it was a big deal as some very strong players remained amateurs - Bobby Jones for instance. Nowadays, most guys jump to the professional ranks as soon as they complete their personal goals (or just go straight to the pros, like Sean O'Hair) whether that be a collegiate championship or an individual one like the US Amateur or Public Links. So the Walker Cup is the place to check out future stars and is for the real afficionados.
Yeah, I agree--I love the Walker Cup, and I think it's scheduling stupidity to put it on the same weekend as the PGA. Like I said before, the PGA and USGA are really screwing up amateur golf in this country.