I always find threads on thread interesting.
Before I knew what I was doing I bought a LOT of Isacord thread (which is polyester) when I bought my used embroidery machine from a business owner off of craigslist. She had over 300 spools for a $1 apiece. DH encouraged me to buy it all. I love all of the color choices I have. I probably use it where many quilters wouldn't think of using it.
Would I do the same thing again if I had the chance... probably not. Because I found that you don't need every color variation of a particular color even for embroidery.