Pretty sure you're limited to 300 blocks. Maybe now that "member behavior" is one of the factors influencing pairing, you won't need to block so many folks.
http://www.chess.com/forum/view/livechess/new-logic-for-auto-pairing-and-seek-graph
Is there a limit to the size of the Block list?
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If 300 is the limit, I'm not able to see more than a 1/2 page using this tablet which is unfortunate. Sometimes I add people to the list to avoid temporarily same-session re-pairing. I only want to play an opponent once. It would be hard to unblock them later if I can't view their name on the list.
As to the auto-pairing logic, I don't like anything I can't control. It may be an improvement but still leaves me less than satisfied. I want an option that players can choose that limits games to those players who mutually agree that disconnects count as a forfeit.
Gosh what a surprise. I was wrong again. It's 200, not 300. 
Sep 25, 2022
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#7
Why does chesscom have a block limit?? I thoroughly enjoy blocking most of you fools I see in the forums. 90% of active accounts on this site are either smurfs or cheaters and I have zero desire of playing them. Even mods can't be blocked. What a disgrace of a site!
Since there seems to be a rather lax attitude towards restricting people who frequently disconnect, I have started adding players who abandon games to my personal block list. Unfortunately there seems to be a limit to the number of players one can block. Is that correct? What is the limit?
Is there any hope chess.com will change their seek parameters to allow people the option to agree to forfeit on disconnect before the game begins?