Imitation is the sincerest form of flattery. Well, maybe not for the folks at online travel company Kayak.com who are now accusing Microsoft's recently launched Bing Travel service of what essentially amounts to Web site design plagiarism.

Kayak has sent a legal letter to Microsoft asking them to alter the site, with the Norwalk, Connecticut company's chief marketing officer telling Wired that: “from the look and feel of their travel product, they seem to agree with our approach to the market.” (Link via PaidContent.org.)

In an emailed statement, Microsoft spokeswoman Whitney Burk denied that there's any sort of copying going on.

“We are discussing the matter with Kayak," she said. "Bing Travel is based on independent development by Microsoft and Farecast.com, which Microsoft acquired in 2008. Any contrary allegations are without merit.”

The most similar elements appear in the left columns where both sites allow consumers to choose non-stop flights, specific travel times and airlines. Interestingly, Farecast -- the Seattle online travel startup that Microsoft gobbled up last year -- utilized many of those design techniques on its site too.

Still, the rub against Microsoft over the years -- whether in Internet search or software products such as Excel -- is that it operates as a follower of innovative ideas.

Is the software giant doing that now in online travel?

You be the judge. Here's Bing Travel's site:

And here is Kayak's travel site:

[Disclosure: Microsoft Bing is presenting sponsor of the upcoming TechFlash Summer BBQ and Ping-Pong Tournament.]