Previously, anyone wishing to send a direct - i.e. private - message to a user on Twitter had to fulfill two criteria: they had to 'follow' the message recipient, and the recipient had to follow them back. This was an awkward but in many ways sensible solution to limit the capabilities of spammers and block other unsolicited messages from general users (of course, anyone can still publicly direct tweets without permission).

Unfortunately, this could prove a frustration in the circumstances where direct messaging was genuinely useful, such as looking to send someone an email address or phone number. The person sending the message often had to publicly request the recipient to follow them before they could send the DM. 

Now, Twitter has opted to give users to the option to receive DMs from their followers without the need to follow them back. Although this could theoretically provide spammers with a new avenue for sending bulk messages, it could also prove useful as a private way to contact people who have not made their other contact details widely available. It could also offer a private, more efficient way of dealing with issues between users and businesses.

Before you go sending DMs to your favourite celebrity, be aware the recently introduced option is turned off by default. You can enable it through the main Twitter options menu: