Nothing provided it is an honest and upfront with consent from the user. The problem is vast majority of affiliate links are non-consensual, buried in articles and in the worst case are the reason that pages even exist - "top ten dishwashers", "50 gifts to buy your wife for Christmas" etc. clickbait garbage. I doubt most visitors even understand that's why the pages exist or the financial remuneration they get from making these lists.

So it would not be a bad thing that if a browser to detect an affiliate link and ask you if you wanted to follow it as-is or strip the affiliate info out with a checkbox to remember the decision for the site.