I actually do see a difference. House buns tend to get more space when they are out, whereas most outdoor rabbits get only the hutch + run, which going by the minimum reccommended is at least 36sqft. I dont know about other peoples house buns, but my bedroom is around 160sqft, so he gets a hell of a lot more space in the daytime. Therefore I do feel it is acceptable to keep them in a smaller area (like a dog crate, the largest size of which is 12sqft) for short periods of time, as they get more room when they are out.
However I think the size of the base should reflect the amount of time spent in there. If a rabbit can only come out less than 16 hours a day, you need to provide more than 12sqft, preferably 36sqft.
What really annoys me is when people wont bunny-proof, and so wont leave them unsupervised at all. A house rabbit that gets less than 5 hours out a day should either be outside or in a bigger than 36sqft base. Even a very basic level of bunny-proofing will mean you can leave them for an hour or so.
Personally, my rabbit is kept in a 4ft 8x4ft 8 pen which gives around 20sqft, 24 if you count the shelf. He is in this overnight as he jumps on my head whilst sleeping, he gets 12-18 hours free range a day. He also occasionally goes in there when I'm eating. Next year when I have a lounge he will hopefully get 24hour free-range in that, then the rest of the flat in daytime if he gets over his fear of lino.
It wasnt always the case though, I used to have a 4x2ft base (8sqft) and he got between 6-16 hours out before I bunnyproofed, depending on how much I was working and what my uni hours were. I always ensured he got at least 5 hours out though, even when I worked a 12 hour shift, I stayed up so he could have time out. I do find my previous setup unsatisfactory, but at the same time it wasnt awful when I bunny-proofed and he got minimum 12 hours out a day.
I also feel better knowing that, through habit or not, Barney does actually sleep most of the night, I have observed him when I have done all-nighters for essays. I think we should remember that a lot of people on here do have their buns locked in hutches overnight, so 12sqft.
I personally found that once out all day, Barney soon relaxed and become a lot LESS likely to destroy things, so actually needed less bunnyproofing!
edit: I also wanted to add that I actually find 36sqft (the minimum outdoor housing) too small unless they free-range the garden sometimes too, and have gone to great pains to ensure Barney has more than this when he goes into boarding as it is for a month. He will have 47.5sqft. It is slightly diffrent for me though, as he is a big bun.
