We've recently had a spate of emails lately about weight limits, and a customer asked a while ago whether it was valid that some riders "ride lighter" than others. My answer to that is yes, absolutely.
As an example, I'll go back about 10 years to when I was project managing one of these ubiquitous 5 story mixed retail/residential buildings. The developers were always concerned about noise, and wanted to be sure that your upstairs neighbor walking around wouldn't unduly impact your peaceful home serenity. We mocked up a few insulation types and had people walk around above them to gauge sound transmission. One guy, who goes about 250, was positively dainty and you couldn't hear him at all. Another guy, about 80 pounds less, sounded like a herd of elephants on stampede. This phenomenon absolutely applies to bikes.
Some people are "internally" heavy about their riding. My go-to exemplar of this is reigning Everesting World Champ (for today, at least) Alberto Contador. The guy is a thrasher: tons of standing, lots of rocking the bike, and lots of high torque accelerations. The reason why I say "internally" heavy is that the way he and riders like him impart stress to the wheels is from the hubs out.
Then there are "externally" heavy riders. These people aren't too concerned about hitting stuff and running it over, don't unweight when they go over rough patches, and generally just ride in a fairly tractor-like manner. That's not a value judgment, it just is what it is. You can watch people and know the type I'm talking about. The reason I call these people "externally" heavy is that their wheels are more at risk from things that are "outside" the wheel - potholes, crap road surface, etc. Some riders who are quite light "internally" are quite heavy "externally," and vice versa. It's also very possible for people to be light or heavy both ways.
This phenomenon is a huge confounder in trying to establish weight limits. If a 240 pounder can ride daintily, and a 140 pound rider can ride super heavily, then what good does weight do as an indicator of any of this? Not a whole ton, admittedly. That's a huge part of our relative conservative-ness about this. People often unrealistically claim that your wheels should be spec'd only by someone who's very aware of your riding style. That leaves each of us in this world with between 3 and 12 people who are eligible to build our wheels. We see it as it's our role to make you aware that there are variances, and to tease out of you some info that you might not think to give us on your own. I'll also go back to our relative conservative-ness - then penalty for 4 more spokes is 22g, the penalty for an under built wheel can be much higher. We're not trying to belt-and-suspenders everyone to death, but it does address our lack of enthusiasm over the whole concept of "how few spokes can I get away with."
Have a lovely Monday.