That same wiki article references Google's experienced numbers, with a high end of "about 5 single bit errors in 8 Gigabytes of RAM per hour"

Google at the time was buying memory chips that had failed manufacturer QA, stuffing them on to DIMMs themselves, and then running whatever seemed to pass.

That number was consistent on-the-ground pre-launch and post-launch (with the exception of a short period of higher error instances due to a solar flare).