In 2009 Ken Pomeroy's end-of-season rankings had the Pac-10 as the strongest top-to-bottom conference in the nation. They didn't have any elite teams, but a remarkable 6 of 10 teams heard their name called on Selection Sunday, and five of those teams advanced at least to the round of 32. In the three years since only eight teams total have qualified from the Pac-10/Pac-12, and of those eight only one was better than a 7-seed (Arizona, No. 5 in 2011). In the six years prior to this run they had produced twelve top-4 seeds, including four No. 1s.
The problem has been lack of talent. In the NBA draft following Pomeroy having them at No. 1, the conference produced six 1st round picks (and the first pick in the 2nd round) and three of those picks were top-10. It's been three drafts since then and the conference has barely matched that output. From 2010-2012 it has produced seven 1st rounders, total, and two top-10 picks.
For the power programs - namely UCLA and Arizona - they've been able to recently reload through recruiting. But to be considered among the best conferences in the nation, they need more than two good programs. They need depth. Washington has been the best recently at holding up their end of the bargain.
The Pac-12 currently has 35 players who were consensus top-100 recruits. This is nowhere near the level of the ACC (56) or the SEC (50), but it's close to the Big Ten (40) and the Big-12 (31, distributed among two fewer schools than the Pac-12).
As I've shown before, 24 of 29 1st rounders in 2012 were former consensus top-100 recruits (the 30th player was from overseas). So it matters. It's easy to point to the 3* player who made it big, but it's also rare.
So to find that depth the Pac-12 has been burning it up on the transfer wire. Of those 35 consensus top-100 recruits, only 27 were landed as freshman. That leaves eight (or 23%) which arrived from another school.
UCLA has the trio from North Carolina (the Wear twins and Larry Drew II). And three Wake Forest players have landed in the Pac-12 - there's Tony Woods at Oregon, and Ari Stewart and JT Terrell at USC. USC also brought in Renaldo Woolridge from Tennessee. And Utah has Aaron Dotson from LSU.
And this doesn't even count the numerous transfers who weren't consensus top-100 recruits.
UCLA and Arizona are likely going to lead the resurgence of the Pac-12, but they need the programs below them to carry their weight. For now, the Pac-12 is using transfers to do just that. Of course, many transfers leave schools because of personal troubles. So there's a risk involved. But the Pac-12 has been so bad of late that some risks are necessary.