Let’s face it, not all Twitter users share good things. There are numerous scammers and nefarious folks in Twitter land. To combat this, Twitter allows user to block accounts. This will stop users from adding you to lists and will not show you @replies or mentions from that user. They will not be able to see your profile picture on their Twitter homepage or timeline. Their tweets will still show in a search though. Instructions on blocking someone can be found here.
Yesterday, Twitter announced that you will now be able to share block lists with other Twitter users. You can also import lists from other users. To export your list, you can go to your Twitter settings and on the left hand side there will be an item for Blocked Accounts. You can then choose the Advanced Options. You will then have an option to export or import a list. If you are importing a list, it would need to be in .csv format. Twitter explains more in this article.
This should help the Twitter community ban together to fight spammers, scammers and other shady Twitter users.