Food mogul Nestle has turned to Twitter for an ad campaign to promote JuicyJuice, reports AdAge.

Juicy Juice is not the first brand to integrate Twitter into an ad campaign, but it is the first to allow users to post tweets within an ad unit that appears anywhere on the web.

The ad unit will be tested for one month on mom-targeted sites BabyCenter and CafeMom. Questions will appear in the ad units, such as: How do you stimulate your child's mind? or How important are vitamin-enhanced foods to you? Users can respond with short messages, or tweets, directly in the ad.

If members are logged on to Twitter, the answers are posted directly to the ad; otherwise they will be directed to Twitter.com and asked to sign in. The postings also appear in users' Twitter feeds with a hashtag (the # symbol, used to group keywords or events for simpler searches on the site) to be moderated by Nestle, although there is the option of turning this function off.

Those who actually click on the ad unit are taken to the JuicyJuice YouTube channel, which contains a number of helpful videos on basic food hygiene.

Other brands that have incorporated Twitter into their ad efforts include Skittles and TurboTax. The difference between this campaign and others is that it allows a conversation to take place within the ad unit, rather than just syndicating tweets already posted on Twitter.

Though the ad unit is a paid placement, the additional impressions are effectively earned media, says SocialMedia CEO Seth Goldstein, noting that the hashtag can spark interest when it reaches the tweeters' followers. In line with other Twitter applications, there is no revenue involved with the microblogging service but it could lead to new sign-ups and increased usage.

Last April, Land Rover launched an integrated campaign using Twitter and out-of-home venues like billboards and taxi TVs. The campaign used hashtags in its out-of-home venues to spread word of Land Rover's Twitter effort.

A recent study revealed that more than eight in 10 Twitter users, most of whom represent small businesses, expect their company's use of the popular microblogging tool to increase in the next six months.