How far is too far in detaining potential suspects?

In the rush to solve "terrorism" there are repeatedly stories of horrors visited by the police upon innocent civilians. I think the police are going too far.

Here is one such story: Suspicious behaviour on the tube (David Mery, Thursday September 22, 2005, The Guardian)

The fellow is apparently a tech journalist because he describes the variety of technical gear kept in his apartment that he uses in conducting reviews of technical gear.

The story is that he was returning home for work, and found himself suddenly arrested by the police. He lives in London England, and this was in July shortly after the bombing in the subways system. Around the same time you may recall a Brazilian was shot and killed by London police officers because they suspected him of suspicious activity, but he turned out to be completely innocent.

In this case the police ticked off a list of suspicious activities (quoted from the article):

• they found my behaviour suspicious from direct observation and then from watching me on the CCTV system;
• I went into the station without looking at the police officers at the entrance or by the gates;
• two other men entered the station at about the same time as me;
• I am wearing a jacket "too warm for the season";
• I am carrying a bulky rucksack, and kept my rucksack with me at all times;
• I looked at people coming on the platform;
• I played with my phone and then took a paper from inside my jacket.

Very innocent, but the result is he spent the night in jail, his girlfriend was terrorized first because he didn't show up for their date and that she couldn't reach him, and later because the police raided their apartment. He also had to hire a lawyer (er... soliciter), and now the police are refusing to erase the record of the incident meaning that all police agencies around the world (due to information sharing) will now see his name having a Terrorism indicator in his record. (due to having been arrested for suspicion of terrorism)

er... isn't something wrong with this picture?