I logged into the Plan 28 Twitter account and it suggested that there might be some people that @plan28 would like to follow:
A couple of things are pertinent here. Firstly, @plan28 does not follow anyone (and certainly not me) but oddly Twitter is recommending a number of people to follow and indicating that they are followed by John Graham-Cumming. Clicking on my own name I get taken to my @jgrahamc Twitter account.
So, I'm not sure why Twitter thought @plan28 would care who @jgrahamc follows, but that's not the oddest part.
@jgrahamc does not follow BBC News (UK), TechCrunch, BBC Technology, Stephen Wolfram, or Tim O'Reilly. In fact, from that list @jgrahamc only follows @causata (my former employer). Scrolling further down I see that Twitter claims that @jgrahamc follows Time Magazine, Programming Wisdom, someone called Mikhail, someone called Alex Jamieson, the Mars Curiosity Rover, The Onion, and Douglas Coupland.
I don't follow any of them.
I suspect that Twitter is keeping a list of people I followed in the past (I at least recognize having briefly followed Douglas Coupland and the Mars Curiosity Rover in the past; although I don't recall ever showing interesting in Time Magazine or Stephen Wolfram).
If I'm right that I did follow those people at some point in the past and Twitter has remembered then it highlights, yet again, one of the important facts about Internet companies: their idea of 'delete' or 'stop' or 'sign out' and most people's are not the same.
Because of this it's worth thinking of things you do on the Internet as public and irrevocable.