Honestly, if I ever need to stop or slow down when out shopping I try to have some consideration for my fellow shoppers by looking over my shoulder indicating and pulling over to the left hand side before stopping. Especially if it's really busy and crowded. I don't just suddenly stop (usually in a big huddle of about 4 people) and block everyone's path so they have to pull up with a grinding halt, reverse and walk around me (with a fully laden pushchair).
Grrrr. Had a difficult afternoon as you may gather. Some people are very inconsiderate. Or maybe it's just me BU?