Steam limits the number of friends you can have, but I am uncertain if there is a limit on how many people you can block.
I tried to google it, but information I found was conflicting. Some said it was infinite, others said it was 500, again others said it depended on the Steam Level. However, none of those were from official sources and merely sounded like best guesses.
So is there a limit on how many people you can block on Steam?