A friend of mine went through 7 rounds of interviews for a senior position in a tech company.
The sixth round was actual work, coming up with a preliminary plan for their first 90 days at the company in the position. It took them about a week to pull together and finalize.
The last round was a 15 minute discussion with one of the founders (who has since moved to the board and isn't involved in the day-to-day any more).
About 30 minutes later they got a call from the recruiter saying they "weren't a good personality fit with the founder" and they offered the role to somebody else.