my house is 2200 square feet for a family of 4. It's fine, although were I to build my dream house, I'd go for approx. 2500 sf to have a little more entertaining space in my kitchen/living room area..

Once houses get to 3,000 sq feet, it takes too long to get from the bedroom to the kitchen for that morning cup of coffee!!

We have just over 2500 sq ft for 4 of us, and it is the right size. Our last home was larger, but the floorplan of this one works much better and actually feels like we have more room. The kids would like more room, but I think this is plenty to keep up. I will say having 3 full bathrooms is nice in that the kids each have their own and I don't hear bickering, lol! Come retirement, I definitely want something smaller though. I still want a home with a yard, but something small enough to easily keep up yet large enough for an occassional guest.

My first home when I was in my early 20's was a 400 sf, one BR condo. on Siesta Key. At that time it was just perfect, just enough space for me to move around in and at that point in my life I spent a lot of free time on the beach. Now, 30 years later and married we have a much larger home (about 3300sf of living space with the obligatory 3 car garage). It's a great house but whether or not you have a small home or a large one, you can only be in one place at a time. Also, my wife and I have the largest home among our family members so whenever there is a family dinner or activity it is almost always at our house since we have the most space. It also is the source of lodging for out of town family and guests. We enjoy having friends and family visit but it was an unintended consequence of moving into a larger home.
My guess is that, just as what happened a couple decades ago, with higher energy prices, higher interest rates and possibly weaker economy that people will scale down and the typical home will get a bit smaller once again.

I live in the northeast with a husband and two kids, and plenty of my friends and/or acquaintances live in what have been referred to here as McMansions. And I must say that they are filled with nuclear families not as JJ generalizes large, extended families.

JJ, I'm not judging, you probably have great reasons for needing a big house and if you enjoy it, that's great. But the American family IS getting smaller and people who take in relatives for large chunks of the year are much rarer than those who live in a typical nuclear family arrangement. I'm willing to go so far as to believe that SOME of the folks who buy really big houses house parents, cousins, etc. but to put that out there as the justificiation for a trend to larger houses seems far-fetched.