It really shouldn’t happen at all. It is not that difficult to be careful of the links you click on. These sorts of things have been doing the rounds for years. Some people have responded to the spam, with some interesting comments.
I particularly like Laura’s reply.
Though, the best one has to be the Internet Party. If you are going to be on Twitter, as a public figure, learn the common pitfalls. Don’t click on links that you aren’t certain of.