So far my experiences in street photography have been rather pleasant. Then again I've only been shooting in the street for abt 6 mths now...
Most of my shooting are in areas where tourists frequent, so I suppose it is not unusual to see someone with a camera aiming off at passer-bys (especially if you are carrying a DSLR). People just tend to give a cursory glance to see if you are acting suspiciously or not. For example, if you're taking photos of kids playing around at the Bugis waterfall, parents would generally ignore you or sometimes even ask their kids to smile for the camera! Having said that, I'm usually a bit cautious when taking shots of children (lest some parents think that I'm a paedophile!). Bottom line is, if your intentions are good (at least in their eyes), you probably won't get a negative response.
My take on STOMP is that people on tend to react to their photo being taken if they are doing something illegal or socially unacceptable. And I suppose that would be the natural reaction for anyone in that situation. People in general are becoming more aware of how photographs of them in uncompromising circumstances could be used against them in court or to hurt their reputation.