it means if you visit a website they could know exactly who you are, might not be an annoyance when it's a technology startups homepage but what if it's a porno

it means if you visit a website they could know exactly who you are, might not be an annoyance when it's a technology startups homepage but what if it's a pornography site, or a site for an engagement ring, or a surprise holiday you're planning? There's lots of examples where this could be a concern. Anything with questionable legality (eg: piracy) would be a more pressing concern.