There's a couple of different sorts blocks. If someone is "hacking" or cheating, their account is closed, not blocked - they can't log on or play here any more.
Aborting too many Live Chess games can lead to a 5 minute block before you can play another game - see Sportsmanship Policy - Chess.com Member Support and FAQs
How long could I be blocked if I abort the games?
If one person was blocked by using hacks, how long could he play again?
Does Chess.com have unlimited block? or is it always for a limited time?