In the early days of auto racing there were maximum weight limits--it was thought that more weight -> bigger engine -> faster car. Of course now things are just the opposite, to the point that race winners hope to collect enough loose bits of rubber ("marbles") to their super-sticky tires from the track during the victory lap to avoid penalty...

Collecting rubber isn’t about adding weight. The teams want to mask the exact tyre wear amount/patterns, which they do by covering the surface with scraps.

<edit> Actually this seems less clear cut than I thought. I'd heard from David Coulthard's commentary that the reason for picking up was to cover the wear from other teams' eyes. A quick search suggests many people believe it's to do with weight. The weight explanation seems odd, since if the officials think the tyres are masking the true weight of the car, they can demand a different set are used for the weigh-in, but I can't find an authorative source either way.

So it may be to do with weight, or it may be to do with hiding tyre wear. </edit>

Yep. I most certainly did.

I got a 4 year degree in mechanical engineering and worked a full-time job building cars for a bit, and I still wrote down a line that sounds as stupid as it does.

But damn, I did not expect that line to draw as much attention as it did down the thread. Such is life.