Tax Certificate Auctions. Assume I know nothing

I hear tell that I can get tax certificates real cheap at auction or private sale and can either collect the penalties/back tax/interest or I get the property.

  1. Why is this not a great way to get undeveloped land full of sagebrush and tumbleweeds at a low price?

  2. If the seller is not the county, but a private individual (esp. ebay, craigslist, auction house), what are the chances it’s a scam?

  3. I buy a certificate for $50 and the guy never pays. Did I just get 1000 acres of wasteland for $50 or are there added fees?

  4. What are my legal obligations (I know - jurisdictions may vary) to notify the property holder of the tax debt?

Anything else I don’t know enough to ask?