I've seen this all over the place and firmly believe that it's a made up statistic. I also don't think it's exclusive to the 1-series. I bet that the vast majority of 3-series owners think the exact same thing and I bet it would be worse since that is the ultimate "I just got promoted" car. The 1-series, at least in the US, is much more of an enthusiasts car than the 3-series (estimating the ratio of enthusiasts to units sold) which makes me really think this 80% is total horseshit.
FWIW, Not a single person on the 1-series forum participated in a poll of any kind. That's well over 1,000 people.