I'm sure you are looking at more than just URLs. Say you have a lead form with two fields, email and zip code. You would store a variety of data points besides

I'm sure you are looking at more than just URLs. Say you have a lead form with two fields, email and zip code. You would store a variety of data points besides those two. Referring URL, IP address, useragent, etc. If you just hash everything, and I gain access to your hashed values, it would be easy to make a lookup table reversing the one-way hash, at least for some of the data points. I haven't had a chance to read the k-anonymity or related papers, but from what I understand it's not specific to data points like age/sex/etc.