Hi, here's an end user perspective. For a few years, a local promoter was also running his own sanctioning body (like OBRA and ABRA). He had a deal where you bought a year's worth of entries (it was a very good deal if you raced a lot) and you got a permanent, cloth number. I did that for two years and I liked it.
I liked:
Being able to pin on my number the night before
Having the same number for all of his races -- no more, "What number am I?"
Not having to add excessively to my box full of numbers in my garage
The promoter dealt with
People without permanent numbers, which was the majority of racers
People forgetting numbers -- I forgot once and they gave me the same number but in Tyvek (which became my spare number)
Since you only got the permanent number if you bought the full year deal, the promoter did not have to with people trying to sneak into races.
Now the promoter does USAC sanctioned races so the permanent numbers are gone. Also, I hate that USAC or our local USAC body (SCNCA) requires a different number for every race. It seems like such a waste. As a rider, pinning on multiple numbers, if I'm doing multiple races, sucks. I presume promoters hate buying so many numbers when they know statistically, certain races have large numbers of people who do multiple races. For instance, a large percent of 55+/65+ guys also race 50+ at criteriums where they schedule those categories. That's something like 30 racers. A similar thing happens with 50+ and 45+.
I'd love to have a permanent number again and an alphanumeric or color coding scheme would be fine with me.