Apparently a request for ownership of the account was made by someone (see below for who that might be) representing the museum exhibition space based at the bridge (Tower Bridge Exhibition) and the existing account, along with all of its tweets has now gone.
I won't go into the legal or moral issues - plenty of people are talking about that already - I want to bring a cultural angle to the debate.
What was @towerbridge?
It was a cute mashup between the publicly published schedule for the bridge and a bot that turned that data into tweets created by Tom Armitage. You could see when vessels passed under the bridge and when the bridge opened and closed, amongst other things (spoof conversations with other bridges for instance). A few lines of ruby code and some simple automation and you have a "Spime" - a word coined by science fiction author Bruce Sterling. It was a bridge that talked to you, and for me was the main example I would use when explaining the concept to someone new to it.
Here's an early screengrab of some of its tweets:
The internet of things
So Tower Bridge inadvertently became a tweeting object at a time when lots of people were becoming interested in Sterling's ideas about an 'internet of things' - a future filled with objects that report on their status in some way, where objects could be findable by their locations, data that could be generated and used in interesting ways by simple physical interactions. Wired runs a great series of observations about this area in Spime Watch.
History doesn't stop
Tower Bridge Exhibition self-describes with "A visit to Tower Bridge Exhibition clearly explains how the Bridge works and describes its fascinating history."
Personally, I'd say that a bridge being cited at conferences about the future of how people and technology interact with objects around us, and that people over a period of a few years had unexpected and interesting conversations with and about the bridge, counts as 'fascinating history' and explaining day-to-day how the bridge works.
It seems so short-sighted that a museum has deleted all of this - all of the URLs pointing at this account are now broken. A genuinely interesting part of the bridge's, and the internet's history is now gone, whereas the opposite should have happened - this account should have been included in the museum's activity. People enjoyed the account, it proved an interesting and funny way of humanising the day-to-day operations of the structure in a way that hadn't been done before.
Because history doesn't stop, we want our museums to be 'backing up' what's happening around us, and that includes what's going on online. The modern world is dominated by mobile phones, the web, devices everywhere, and when we look back in future years unless we've kept some of that stuff we are going to have a great big hole labelled 2011 "really interesting stuff happened around that time but nobody had the foresight to keep any of it."
Curators vs Marketers
But herein lies the problem. I doubt the curator (if there is one) or anyone interested in history-in-the-making had anything to do with this. This was a marketing job. Here's a grab of what @brandcarrie (Carolyn Hall, Marketing and Events Executive at Tower Bridge) was up to recently (including ironic 'out of touch' tweet):
Another one of those examples of how not to do "social media". If I thought it would do any good I'd say to them "give the account back", but that doesn't really matter because the content is gone, the URLs would all still be dead, and a little piece of the bridge's history was lost forever because of sad, ignorant, offhand destruction.