Philipp Lenssen lists some problems with doing personalized search. Boiling it all down, Philipp is saying that personalized search is hard to do well and can't ever be perfect, so it's not worth doing.
He's right that personalization is hard. It has to work from noisy, sparse information. It has to deal with changing preferences. It has to avoid pigeonholing. It has to make good predictions. And it has to do it all in real time for millions of users.
And he's right that it can't ever be perfect. Personalization is so hard that it's going to make mistakes. Probably a lot of mistakes.
Does this mean personalization is useless? Of course not. Personalization doesn't have to be perfect. It just has to be good enough.
If personalization helps people find what they need faster on average, it's a win. It doesn't have to be right all the time. It just needs to be helpful.
Take one of the examples from Philipp's critique, someone who searches for the single word "restaurant". If those results aren't targeted to a best guess at your location, they're completely useless. Try it on Google and look at the top results. In the vast majority of cases, it would be more helpful to emphasize your local restaurants than return the generic results. Personalization would be helpful.
Or let's take Amazon.com's personalization. Amazon's personalization is far from perfect, but it doesn't have to be. A generic storefront emphasizing top sellers is much less useful to you than a storefront emphasizing mostly products you like. When Amazon's personalization guesses wrong, it shows you something you didn't want, which is what the generic storefront would have done anyway. In general, their personalization is helpful.
Personalization is hard. Personalized search will make mistakes. And that's okay. It doesn't have to be perfect. It just has to be helpful.