wheel - 2:10 pm on Nov 1, 2011 (gmt 0)
I've seen similiar things twice in the last cuople of days. Buying some cold weather sleeping bags, the user reviews and specs are loaded on the detail page, but not visible until you click on the tab 'user reviews'. That seems fair enough.
I also noticed that I got a backlink from world news on a video page. I can see it when I view the code, but I can't find where to click on the page to actually view my link. Perhaps if I could find the way to make the link visible it would make sense, but darned if I can.
In the end, if the content is visible based on additional user interaction (like a help box) I believe that's considered fair play by Google (just based on what I've read in the past). If it's not intended for the visitor to see, then it's cloaking.
I don't expect in either case that a bit of extra content is likely the key to top rankings on competitive terms.