For many years, Juno has been touted as NASA's "low cost" mission to the Jovian system. As a New Frontiers mission, it is cost capped at only $1 billion.
From its launch in August 2011 to its arrival at Jupiter in July 2016, it spends nearly 5 years in space. Yet, despite all this cost and time, it will only spend a single year orbiting and studying Jupiter.
The Juno mission is set to conclude in October 2017, after completing 33 orbits around Jupiter, when the probe will be de-orbited to burn up in Jupiter's outer atmosphere.
Why waste all that effort, money, and time, on a single year long mission? It does not appear to be due to the radiation environment around Jupiter:
Juno's planned polar orbit is highly ellipitical and takes it close to the poles—within 4,300 kilometers (2,672 mi)—but then far beyond even Callisto's orbit.
This type of orbit helps the craft avoid any long-term contact with Jupiter's radiation belts, which can cause damage to spacecraft electronics and solar panels. The "Juno Radiation Vault", with 1-centimeter-thick titanium walls, will also aid in protecting and shielding Juno's electronics.
Its orbit is optimized to reduce radiation and it has inherited prior design experience from Galileo, which spent 8 years orbiting Jupiter.
Neither does it appear due to be mission funding. Juno will cost $1.1b, but that is predominantly dedicated to design, construction, and launch costs. Traditionally, operations has been a large amount of the mission budget, and NASA has experience with running missions on lean budgets now (see: Opportunity).
Frankly, it seems like a very low science to dollar ratio.
TL;DR: For such an incredible amount of resources that have been expended, why is Juno spending so little time at its target subject?