Social networking: A map of Britain in 140 characters or fewer

Find out what's causing a buzz in 12 different cities with Twitter's latest location filters. Simon Usborne takes the nation's tweeting temperature

Finally, more than six years after Twitter launched to become the most global of social networks, users in Portsmouth have the chance to discover what their fellow tweeters are going on about. The city was one of 12 in Britain (see map) to be given local trending filters yesterday, revealing the digital pulse of sites across the UK.

What new insights could we gain about the residents of Hampshire's second-largest city? Precisely none: according to a Twitter tour of Britain conducted at lunchtime, users everywhere were talking about the same, boring stuff.

But before we write off this bold attempt at localism, what is a Twitter trend? Skip the following paragraph if you already know.

Each user is presented on his or her home page with a list of the words and phrases mentioned most often on the site at that time. Many of these terms take the form of hashtags, or phrases marked with the # symbol. For example, #starbucks was trending yesterday. Anyone clicking on the hashtag was taken to a stream of the things people were saying about the chain's tax affairs. Got it?

One could already switch between global and more local trending lists, including those for the UK, London and Manchester. Now, to make it "easier than ever before to find out what's going on in your area and to get involved in the conversations", Twitter has added a dozen more filters.

Perhaps this will become useful during big local-news events or football matches, but there were only two significant regional quirks in the lists yesterday. "#fmq" topped trends in Edinburgh but didn't feature anywhere else (which makes sense – it stands for First Minister's Questions, Alex Salmond's weekly grilling). More intriguingly, "Grammy" (as in the awards, nominations for which were announced yesterday) was most discussed in Liverpool but didn't get a look-in in any other city. An investigation could not reveal a reason for Liverpool's particular interest in the awards.

Otherwise, lists variously revealed chat about Max Clifford as well as Oriol Romeu, a Chelsea footballer who was taking part in a Q&A run by the club under the hashtag #AskOriol.

When they are or aren't revealing geographical trends in online discussion, trends have caused controversy. Corporations find to their cost that promoted terms are vulnerable to hijacking. When McDonald's coined #McDStories in January to dispense good news about its brand, millions did the opposite. When Susan Boyle's record company tried to promote a new album, meanwhile, users read "#susanalbumparty" in alternative ways, which proved to be amusing whether you lived in Portsmouth or Porto.