Twitter may have taken the development of a business model slow, but its efforts to monetize its 140m user strong audience are in full swing.

Earlier this year, it opened up its long-anticipated self-serve ad platform, and offered US businesses $100 in free advertising credits to businesses in partnership with Amex.

Today, in an effort to bolster its business on the other side of the pond, Twitter announced a potentially sweet deal for UK businesses: tweet about how you’ve been using Twitter and you could win £1,000 in free advertising credits.

The Twitter blog has the details:

Tweet using the hashtag #ukbizstories and tell us how you’ve seen a local business use Twitter creatively to connect with the community and reach their customers. We’d also love to hear from local business owners directly about how you’ve used Twitter to engage your customers.

We’ll select and reward the businesses with the best examples with up to £1,000 free Twitter advertising credit to be used for our Promoted Products.

The contest ends on July 31, 2012. Twitter does not state how many £1,000 prizes will be awarded, but its terms give it the ability to use all testimonials submitted. That means the promotion could be a very cost-effective way for Twitter to get business to vouch for it.

The potential problem for the company: given that its self-serve advertising platform hasn’t been around for long, many of the testimonials it’s likely to obtain will speak to Twitter in the context of earned media, not in the context of paid advertising. This, incidentally, is shaping up as a problem for Facebook too.

While Twitter arguably benefits from the presence of brands and businesses which use free Twitter accounts to interact with consumers and customers, testimonials speaking to this may not be all that effective at convincing other businesses that paid media on Twitter is the way to go.

In fact, the best testimonials could convince some businesses that a free Twitter account is so effective, paid ads on Twitter are unnecessary. With this in mind, it will be interesting to see just which testimonials Twitter selects and chooses to highlight.