You probably don't want too much fructose. A young guy keeping it below about 40 grams is probably okay. But some experts say 25 grams max. Of course, cranberry is not very sweet, so you'll have to check that out.
Even so, remember that juices are very powerful. I'm not saying it's bad for you, but I think it's always better to eat a well-rounded, whole foods diet trying to not overemphasize any one food (or drink).
For example, did you know that cranberry is an iron chelator?
BioFactors, Volume 37, Issue 2, pages 121–130, March/April 2011, "Iron chelation by cranberry juice and its impact on Escherichia coli growth"
It is so powerful that in the above study, it actually inhibits E. Coli growth. So a lot of cranberry juice can have actual clinical effects and I am not sure we really understand all of them. And keep in mind that our ancestors at fruit, not the juice squeezed out of a pile of them.
I have no doubt juice is good for you, and, as you know, recommend a few in my book. But I also point out not to "go crazy."
Also, you can read here about how Tim Ferris is anti-juice and why:http://www.peaktestosterone.com/Anti-Juice.aspx