Twitter has announced that it is to begin showing Promoted Tweets to mobile users who don’t follow the advertiser’s feed.

The social network has also added new targeting tools that allow advertisers to target their messages to desktop computers and laptops or specifically to mobile devices.

A blog post states that since launching Promoted Tweets and Accounts in its mobile apps last month “reactions have been positive.”

However the sponsored tweets have up till now only been shown to users who follow the advertiser – as of today it will be expanded to “mobile users that share similar interests with their existing followers.”

The post doesn’t go into detail about how these interests will be determined, but it could feasibly just be based on other accounts a user follows.

So, for example, Coca-Cola ads could be shown to people who follow Pepsi’s account.

Twitter has also introduced new targeting options, so advertisers can pinpoint iOS, Android or other mobile devices.

In the same post referenced above, the company uses the example that mobile game and app sellers can now target users who are likely to buy their products.

This sounds like it could be an extremely useful tool for marketers that want to limit their spend, and focus on certain demographics rather than delivering ads to all users.

However the headline news is the fact that Promoted Tweets are being expanded to mobile – as this is something that Twitter (and also Facebook) has historically shied away from.

The initial justification for introducing Promoted Tweets into mobile timelines was to “ensure that people see important tweets from the brands they care about.”

But this latest move means people will see tweets from brands they don’t care about.

It all boils down to the fact that Twitter needs to get better at making money from its 100m active users, 55% of which log in through a mobile device.

Last month it opened up its self-serve ad platform to 10,000 new customers, and the expansion of Promoted Tweets on mobile is another step to make its ad platform more attractive to brands.

Promoted Tweets are fairly inoffensive, so it’s unlikely that users will be concerned – but it is interesting to see how cautious Twitter and Facebook are still being when it comes to monetisation.

It seems that both are all too aware that despite their popularity, one major slip up and users could begin to shift their focus to a new social network. Google+ anyone?