I never checked before until just now. 55 in the last 90 days. So that's about more than 1 cancellation every two days. I wonder if this number would be this high if ebay didn't decide to welcome (nay, encourage) buyers to cancel their orders. Let's also include UPIs in here... doesn't matter to me since I don't have auctions.
The days where ebay told the buyer their bid or BIN (pre-IPR) is a contract are loooooooooooooong gone.