Tax sales are a balancing act among (1) the need of government to collect property taxes and, if owners will not pay then, then to provide incentives for investors to purchase the tax rights and (2) investors, who need an attractive return for the risk they are taking, and (3) citizen taxpayers, who should not lose their property and all equity because of small debts and perhaps temporary or at least relatively short term financial difficulties. So, no one group is the primary focus of the laws. Nobody is targeted for "protection" to the complete detriment of someone else.
Sometimes taxpayers, or their heirs, have moved away from the neighborhood. Nobody knows where they are. They do not receive notices about the tax sales. Their friends do not call them when the notices run in the newspaper. Perhaps it is a person who has been overseas in the foreign service or the military or missionary or Peace Corps service. They intend to come home to "Mom and Dad's" old house, eventually, but it is not top of mind. They assume other family members are looking after things. It turns out nobody is looking after things.
The tax sale happens. An investor buys the liens, thinking he/she will end up with a property worth, in its current condition, perhaps $40,000. That missing person, in all fairness, is entitled to the equity over and above the taxes, interest, legal expenses and auction expenses. That is because of the United States Constitution, and all state constitutions. Plus age-old notions of fairness.
If that missing person does not know about the tax lien foreclosure, they cannot appear and demand an auction. Perhaps that missing person could not afford to fix the property up, and so they would not redeem, even if they knew, but they are certainly entitled to the equity.
It is the Guardian ad Litem's job, and ethical responsibility, to protect the rights of those people who cannot protect their own rights. Historically that has been people like minor children, mental incompetents, and unknown people who do not even know that something bad is about to happen.
In my opinion, in order to protect the rights of the unknown defendants, the GAL must always demand an auction. The unknown people have that right, if only they knew about the lawsuit. It is the GAL's job to do what those unknown people would have done, if they could.
The auction is public, and advertised in the paper just like bank foreclosure auctions. Anybody can bid. The investor has the opening bid, in the amount of the taxes and other legal charges. If someone bids more than that, the investor can bid against them. The investor has an advantage because he/she has already spent the money and accrued the interest for the opening bid. Any other bidder has to write a check for that amount, PLUS the amount over that to reach their winning bid. If the opening bid is $8,000 and the bidding reaches $15,000, a 3rd party has to write a check for $15,000. The original bidder need write a check for only $7,000, making it easier than a $15,000 decision.
Investors should not get emotionally attached to their tax sale properties. No investor should get emotionally attached to real estate. Lose out to a 3rd party bidder on the property for which you bought the tax liens? Go to some other investor's public auction and bid on THEIR property. There will be plenty to go around.