It's a mind-game being played out all over the Tube network, and indeed on many trains and buses throughout the country. It's performed in silence, with people unsure of their neighbours' motives and guilty about their own feelings of suspicion.
Even though people say little when they're travelling, there's plenty going on inside - fears of danger, changed routes, calculations to avoid risks, guilt at making stereotypical assumptions, anger at being unfairly distrusted.
"I do not take my rucksack to work anymore, which had my lunch and work shirt. I would rather wear a dirty shirt left at work than be looked at suspiciously. I also wear a T-shirt to work now, as I am afraid to wear too much, after the shooting," he writes.
"As I got on the tube with my rucksack, a fellow passenger saw me, waited a second then got up, to wait on the platform for the next train," writes Dev.South Asian and Middle Eastern-looking commuters with large bags, as one might imagine, are feeling the brunt of the distrust:
Marcus, who says his family are Greek-Cypriot, has devised a strategy to avoid "odd looks" on the Tube (which he attributes to his Mediterranean appearance). To make himself seem non-threatening, he now wears a Make Poverty History wristband and makes a point of reading the Economist.
I can't avoid carrying a big rucksack with my mobile office in when I travel. As I'm an Asian male that's been getting suspicious looks, I've taken to carrying a bottle of wine as if I'm taking it home for dinner. It's ironic, I don't even like wine, but it's a clear visual symbol that says I'm not a fanatic Islamic bomber.
Of course, now that the secret's out, the next crop of suicide bombers could well be queueing up for Make Poverty History armbands, wine bottles and other non-threatening-looking props.
There are also people who have stopped wearing their MP3 players or iPods because of worries about trailing wires or not hearing orders from the police.
Though, OTOH, one of the original bombing victims reportedly retained her hearing because of the iPod earphones she was wearing shielding her ears (and her life because the laptop on her back took the brunt of the blast). Perhaps Apple should use her in an ad campaign?