Had a multi-month team matching phase followed by a 4-day exploding offer for ~50% below market and got blacklisted for a year or more when I didn't sign it. Great.
The blacklisted for a year thing sounds like the normal Google, “Try again in a year” messaging that happens whenever someone doesn’t get an offer for failing interviews. Again, don’t know if that is what happened, but it hardly constitutes anything nefarious.
To be clear, this is the "You are not permitted to apply for any positions at this company" messaging for people who pass interviews and fail to sign offers within 4 days.
Hiring processed has changed though, so I'm not sure if this is still true.
Never heard of anything like this in the non-startup industry