Here's the lowdown on propriety hops, at least as I understand it. Both the good and the bad.
The USDA used to have a fairly extensive hop breeding program that produced some of the classic craft brewing hops we know: Cascade, Willamette, Chinook, etc.
I haven't looked into why most of the interesting Hop varieties have been coming from private farms in the past 15 years; it could simply be because they are spending more money on hop breeding and the USDA has cut back, I'm not sure.... But mostly all the popular aroma hops that have been released in recent years have been from private farms.
These hop farmers work fairly hard on breeding new and interesting hop varieties. The Hop Brewing Company (joint venture of the select botanicals group (yakima chief ranches), and someone else) claim they cross over 50 cultivars per year, and screen ten's of thousands of hop genotypes. My understanding is that out of hundreds and hundreds of potential hop varieties only a handful even get the potential to be released. They say it takes something like 6-10 years for a new hop to come to market.
So after a considerable about of work, these farmers want that their new hop variety to be exclusively theirs, hence the patents on hops.
The good side of this is, farmers are working very hard to produce new and exciting aroma hops because if they create a great hop, and the demand is strong, and they have exclusive rights.
The down side is, the farms that hold the patents on these hops can control which farmers can grow their variety, and which can't. There are a BOAT LOAD of farmers growing our favorite proprietary hops (simcoe, amarillo, citra, warrior, etc), but obviously not as many as the current market demand dictates. And because of that, spot prices are way up.
Unfortunately it's just going to be the name of the game for awhile with the new hop breeds. Citra is a great example. The Hop farmers are reluctant to tear up acres of their current hops to plant a new variety where the demand is unknown. Citra hits the scene around 2008, and there was decent demand for it. Once Sierra Nevada used it in their Torpedo, and enough brewers got to try it, demand exploded. Because we're dealing with an agricultural product, and one where the plant takes a couple years to mature, there is a couple year lag before supply can catch up to demand. Combine that with a booming craft beer market where IPAs and hop-forward beers are popular, and you can see why these hops are hard to get a hold of.
There definitely isn't a hop shortage. All of the old, standby hops are easy to get a hold of, it's just hard to get Amarillo, Simcoe, and Citra at the moment. HopUnion realizes that, and it's one of the reasons they are producing new hop blends specially targeted at IPAs to help reduce the demand for the hard-to-get proprietary hops. And in a couple years, these hops will probably be easier to get our hands on, just as another new 'hot' hop hits the market.