How did people find my instagram account?

[William]

Okay, so I recently opened an instagram account and I did the feature where it could find people or me to follow based on my facebook friends. I went through that and followed about seven people. I didn't want to follow too many people, because I didn't want to many followers before I really felt comfortable with the application. Anyway, by the end of the day, pretty much all of my facebook friends were following me, even the ones who would have no connections to the people I followed. Did instagram post something to Facebook? I'm not seeing any evidence of that, but it's the only explanation I have.