In the olden days (pre 1996?) the new WDC swapped numbers with the previous WDC, the rest of the grid stayed as they were.
Ferrari had cars 1 and 2 in 1980 (Schekter won the WDC in 1979). In 1980, Alan Jones won the WDC driving car 27. So in 1981, Jones' team (Williams) had cars 1 and 2, and Ferrari inherited the old Williams numbers of 27 and 28.
They next changed numbers when Prost brought number 1 with him in 1990 and McL took 27 & 28. Interestingly they swapped back to 27 & 28 in 1991 when Senna won the WDC. They stuck with those numbers until Schumacher brought the number 1 in 1996. From then on, the number changed each year with the WCC rankings.*
So the reason Ferrari stuck on 27 and 28 wasn't sentimental or superstition, it was because they didn't have a WDC driver.
The old method applied in 2010 would give Jensen's team (McLaren) 1 and 2, and Brawn would stay on 22 and 23.
ps - Villeneuve drove both numbers 11 and 12 in 1977. He drove number 12 in 78 & 79, number 2 in 80, and 27 in 81 and 82.
*edit - corrected the bit about Prost.
Last edited by richard_leeds on Mon Nov 23, 2009 1:31 pm, edited 2 times in total.