Here's a particularly interesting question in today's P-G Q+A:
Ryan Kasun of Export
Yes, there is, and Dejan Kovacevic's answer doesn't completely explain why, so I'll chime in here.
In the past several years, it has not been uncommon for teams to be without one of their A-ball teams for a year. The Astros, for example, had no High-A affiliate in 2002, so they had to skip some of their players straight from Low-A to Class AA Round Rock. It's hard to say exactly what effect this had on their players, of course, but several of those who made the leap struggled at first, including prospects Chris Burke, John Buck, Rodrigo Rosario, Mike Nannini and Darwin Peguero. (Kirk Saarloos, Chad Qualls and Henri Stanley made the jump and did fine.) Burke and Buck eventually made it to the big leagues, but Nannini and Peguero never did. Rosario only got a cup of coffee. Even Buck did not hit especially well again until 2004.
Prospects fail for lots of reasons, of course, and so it's hard to pin some of these guys' failures directly on the Astros' lack of a High-A affiliate, but the point here is that this is really not an area where the Pirates should be cutting corners. Forcing prospects to skip levels when they're not ready to does not help them. If the Pirates are filling their A-ball rosters with over-aged players, then the solution, as Kovacevic suggests, is not to shut down an affiliate, but rather to get more prospects.