An example of personalization that has stuck with me in my own experience as a buyer was a Fabletics questionnaire that asked me what products I was looking for including and not limited to, type of clothing, size, color fabrics, use, etc. It was a very long quiz or personalization option and was enjoyable until I had to enter my email to get the recommended results. Personalization should be specific, but also accessible. I left the site and did not purchase any Fabletics products. My goal was to shop and browse products, and I was not willing to sign up for an account/email just to be able to do something so simple.
Their personalization was a great concept, but I think it may deter new customers who just want to see what products you offer.
I would have changed this personalization by allowing my user to browse after they completed an extensive personalization quiz, however, to connect with them I would add a pop-up to remind them that if they add their email they can save their personalization and not lose it the next time they visit the website.