This is actually not a terrible idea. The vast majority of auto emissions today come from a relative handful of vehicles. Its probably cheaper to "buy" them off of people than it is to spend millions on innefective smog testing systems.
I agree. Whenever I see an old beater blowing clouds of thick blue smoke I wish the police would just pull them over.
---of course,the "environmentalists" shot it down---
Late to the party but here's some data that debunks this BS. Here's a web site that provides some data based on mileage http://www.aircarecolorado.com/repair/acnews/apr99.htm
<5K miles 3g/mi
<50K miles 4.6g/mi
<70K miles 6.7g/mi
<80K miles 13g/mi
Looks like on average vehicles under 80K emit 5g/mi while vehicles over 80K emit 13g/mi. As a vehicles accumulates miles it's emissions go up. Not rocket science. There are roughly 30-40 million vehicles in California. Lets assume each drives 15K miles per year. That's probably conservative. The older vehicles probably accumulate significantly less mileage per year.
35 million vehicles x 15Kmiles/year x 5g/mi = 2.625x10^9 kilograms
15K vehicles x 15Kmiles/year x 13g/mi = 2.925x10^6 kilograms
The 15K "old" vehicles represent a 1% or less problem. The Governor wants to spend $150 MILLON on a 1% change in emissions. Most likely some of the vehicles turned in for the $1K aren't even on the road and are really parts cars for collectors. I bet a detailed study would come up with numbers <0.5%. No wonder California has a spending problem.