The founders of Twitter, the micro-blogging service that has become a media sensation this year, have opened talks with Google about a tie-up, and speculation is rampant that they could be prepared to sell out to the internet goliath.

Rumours of an impending takeover, which would turn its three thirtysomething founders into millionaires many times over, were sparked by a report on the Silicon Valley blog TechCrunch, and spread round the internet in the time it takes to type 140 characters. This is the limit for a single "tweet", the name given to a posting on the Twitter service, which is now used by more than 7 million people in the US alone.

Twitter was valued at US$250m when it raised money earlier this year, and its explosive growth suggests that Google could be willing to pay a multiple of that figure.

In the UK, where the comedian Stephen Fry is the most famous prolific tweeter, its users have grown tenfold over the past year, while celebrities, politicians and businesses are increasingly using the service as a way of communicating with the public.

Biz Stone, Twitter's co-founder and creative director, said yesterday that the team was committed to building "a profitable independent company - and we're just getting started".

But he added a non-denial denial of the TechCrunch story that only fuelled more discussion.

"It should come as no surprise that Twitter engages in discussions with other companies regularly and on a variety of subjects."

Google declined to comment, and other Silicon Valley commentators speculated that the search engine giant is only interested in a partnership deal.

Twitter was founded two years ago by a trio of Silicon Valley entrepreneurs who hatched the idea of allowing people to share text-message-length status updates on the internet and mobile phones. Jack Dorsey, who is now Twitter's chairman, had previously been exploring business ideas in podcasting and software for courier firms.

Evan Williams, now 37, had previous worked for Google after it bought his Blogger blogging software, and Biz Stone has published two books on social media. All three stand to share a huge windfall when Twitter is sold.

A sale to Google is the ultimate cash-in for budding entrepreneurs in the crowded technology industry, and many look enviously at the founders of YouTube, which was bought by Google for $1.65bn in 2006, despite never having made a penny in profit.

Outsiders have been mystified, too, about how Twitter will make money, since its service is free to all.

"Now is the time for Twitter to sell," says Jeff Mann, vice-president at the research firm Gartner.

"It is at the top of its hype range now. Monetising on its own would be a long, hard slog. Twitter's value is in its content, growing by 6 million tweets per day, and it is attractive because it has built a constantly growing, twitching, seething real-time source of comments, news and opinions."