Thank you Lauda:  https://en.wikipedia.org/wiki/Quadratic_growth ... ouchie; so if a 1MB block with y transactions in it takes x seconds to validate then 32 similar 1MB blocks will take about 32x seconds but a 32MB block can be expected to take about (32y)²x seconds.  Or is the quadratic growth on something other than transaction count?

In 2MB blocks, a 2MB transaction can be constructed that may take over 10 minutes to validate which opens up dangerous denial-of-service attack vectors.

So how bad is it? There was a block consisting of one transaction in the coinbase, it was broadcasted about one month ago. It was f2pool that was clearing up a bunch of spam on the blockchain. The problem is that this block takes 30 seconds to validate. It's a 990 kilobyte transaction. It contains about 500,000 signature operations, which each time serializes the entire 1 MB transaction out, moves buffers around, then serializes it, then hashes it, it creates 1.25 GB. The bitcoin serializer is not fast, it's about where 60% of the validation time was. So 30 seconds to validate and that's on a beefy computer, I don't know what that is on a raspberrypi, it's not linear it's quadratic scaling... If you are doing 8 MB, then it's 2 hours and 8 minutes. There are some ways that gavinandresen has proposed that this can be fixed. This transaction would be considered non-standard on the network now, but miners can still generate these transactions.