Now there are massive blocking of Twitter accounts.
Most often, block accounts when you to use mass-following. Blocks is forever!
Also do not use hashtags #ICO #Cryptocurrency etc
Be careful!
UPD
Some accounts of my friends that have been blocked marked "forever" are now unlocked
But anyway, I think we need to be careful
Yes, We need to be careful. I experienced that when I shared many tweets from the ICO page on twitter, And I need to verify my account using my mobile number and once I verified they unlock again. But also take care to your twitter account without binding on the mobile because they can lock forever.