I have been contacted twice in the past year by Microsoft rep's who both told me that one of my products is among the top installed add-ins for Excel (they didn't say top "X", just "top" - but I'll take it). I assume they collect this data via telemetry.

What bothered me is that when I asked questions back, I would get no reply. If they are going to collect this data, the least they could do is help developers out with some aggregate data. I've been selling this product for 10+ years, and to this day, I still vacillate on which version of the .NET framework to target.