That's an interesting question. But it's one for Valve and the owners of the linked websites.
Edit: To expand on this a bit. The script doesn't uncover any private data. If your steam profile is set to private it will stop some information being exposed, but not all. Info about servers someone is on, profile info, tf2 items, friends info.. these are all things that can be blocked using the privacy controls on your steam profile. Vac bans, gameplay info since last reset (imho this one should be blocked if private really), your profile on a comp TF2 site if you have entered one.. nothing you can really do about those.
For the most part you can replicant any function on this script with a steamid and google (one of the reasons for making this script is that I am bored of doing exactly that). If you are concerned about your privacy, I'd advise setting your profile to Friends Only or Private. It greatly restricts the amount of info shown about you as can be seen with the xml from a public profile and a private profile. It also blocks any data from being reported with the Steam Web API (GetUserStatsForGame is the only function I've noticed that ignores this - informed Valve of it several months ago).