We only own 2 acres, which is plenty for sure. Out in the country, dogs that wander off beyond their own property have a nasty habit of getting shot when they wind up at others' places, bother livestock, etc... Now sure, that's not fair to the dog who doesn't know better most times, but it's a reality I intend to protect my dog from. Not to mention the fact that it is pretty inconsiderate (and a potential liability) to let your dog roam onto other people's property (to do what dogs do, relieve themselves, dig, chase the neighbor's cat, etc). Also, we live on a fairly well traveled, paved road, so there is that danger factor too. I have considered installing a radio fence around the perimeter, and may do so to keep her contained when she's playing in the yard (Usually she can behave for about a 1/2 hour while I'm working in the shop or something before she decides that I'm not paying attention enough to catch her wandering over to the neighbor's backyard or out accross the other neighbor's bean field to "investigate" that old hog building...) Those systems have their shortcomings and I wouldn't trust them during the day when we're gone, especially given the traffic on the highway.
Our dog gets to run outside in the afternoons/evenings. She also spends roughly half of all nights sleeping in our bedroom (more often during the summer and winter or when they're forcasting a storm that night). Probably 25% of the time, we'll let her stay in only to have her wake me up at 1 a.m. and ask to go back outside (summer, winter, doesn't matter). And when let out of the basement patio door at 1 a.m, she makes a beeline to her kennel and waits at the door without being told to go there. In the mornings after she's spent the night in her kennel/doghouse, I go out and let her out for a little bit while I refill the water, fill up the food, etc. Most mornings, I have to practically beg her to go out and run around, pee, etc. Otherwise, she'll hop out when I open the door, then hop right back in and sit down. So I think she's ok with the 10x10 kennel. She has an old basketball in there that she can bat around and chase (when not chasing her own tail that is) during the day. A crate in the house would not afford her nearly that much room to move around and entertain herself during the day.