When I was in Peru, I saw some folks in the country raising them in a blocked-off pen very like the one shown in the link, but it was just one big pen with probably 150 guinea pigs in it. I had wondered why the Peruvians call them cuy - but when you get that many together, it makes sense - they say "Coo-EE!" over and over again to each other.

I only tried one once in a restaurant - a medium-fancy restaurant, and whatever herbs they roasted in the body cavity gave it a really overpowering anise/licorice taste - I couldn't enjoy it. But I bet it does taste good when prepared in a different way.