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
I am doing this on one of my accounts but so far it is still safe, I guess frequency has something to do with this if you varied your post and not concentrate in one hashtag your account will be safe and of course tweeting multiple times in a minute is not safe also.