On 9th Sep, my father's wallet was stolen on a bus at Gent-Sint-Pieters station.
Thing goes like this: two women went on a bus and developed some problem with their tickets or whatever that could attract people's attention. Then, another young girl, who pretended lining up with a few euros in her hand and a jacket hanging onto her arm, sneaked her fingers into others bag or pockets. When she got what she wanted, she would leave the bus just like being inpatient with those two troublesome women. And, her two fellows would make some excuse to leave the bus as well.
Considering the race issues, I should not describe specifically about their appearance. And, of course, they would change their cloth. So, just beware of uncommon events, such as people who speak fluent Flemish or French and dress unlike tourists, but seem too unfamiliar with the local bus/train/tram system. Also, beware of people who get too close to you no matter how many people are there. Then, last suggestion is, (for women) carrying a bag with many zippers ,and (for men) never never NEVER put your wallet in your back-pocket.