Twitter has been making some more hires recently – first up is Robin Sloan, who joins to handle media partnerships. Sloan previously worked as a strategist and executive at Current TV. During the first presidential debate of 2008, Sloan built an application to overlay tweets on the bottom of the screen. Spookily he was also the author of Twitter’s 5 billionth tweet.

Also joining is user experience designer Mark Otto, who worked at ZURB, an interaction design firm whose listed clients include TinyPic and CC:Betty. And finally Dan Webb, the London web developer behind Twaudio, which brought MP3s to Twitter through direct uploads or recording.

(Hat tips to Venturebeat and Louis Gray)

Louis estimates the total number at Twitter to be around 158 following a regular weekly pattern of hiring. It seems as if the desire to evolve and most importantly monetise, will be the main drivers. After all, the user experience of the Twitter website hasn’t changed in great detail for some time (The main added features have been the new Retweets and Location), and meanwhile 3rd party clients are constantly finding new ways to improve on the default experience.

Beyond the UI for consumers, this could really be about improving the experience for the monetisable advertisers, marketers and customer service teams. Big businesses are generally used to working with well-polished, expensive systems, and polished controls/dashboards for business use will add to the draw for mainstream business.