Quote from @Ashish D.:

I've read through hundreds of post on this website about Tax Liens and Tax Deeds, and almost every single one is discouraging investing into it stating myriad of different problems and nuances. However, when you search the internet, you find hundreds of posts and documentation talking about investors being so successful with it, big ones and small. I've spoken to few investors who have made tens of properties using it. Why are posts and documentation on this website particularly advising against them?

EVERY aspect of real estate investing has been over hyped, over sold, and over simplified.  There is money to be made in EVERY strategy; however, not by EVERYONE.  Almost all require the following in some combination to execute successfully on a sustainable basis : (1) CAPITAL (2) KNOWLEDGE (3) EXPERIENCE.  The gurus” selling mentorship’s and “canned” programs to a inexperienced investor oversimplify the strategy; ignore the difficulty; incorrectly claim that the education they provide is sufficient for success; lie about their own qualifications and experience and success; belittle “real” business/financial/real estate education and provide a totally unrealistic picture of lifestyle, effort, and chance of succeeding.  

The people I’ve encountered in my 40 + years as a real estate investor and private lender who are successful have the following in common
They are educated as to principles of real estate; real estate law; and real estate finance
They LEARN something new about real estate investing almost every day, and are open to realigning their strategy, tactics, and portfolio to encompass new information and knowledge
They SPECIALIZE either in a strategy, property type or geographical area, and become EXPERT in that area
They have survived real estate “depressions” where property prices have dropped 20% - 50%
They understand the difference between real estate investing, operating a real estate BUSINESS, and having a real estate job.
They network, for knowledge, capital and most importantly DEAL FLOW

The key thing to consider when you watch a YouTube video, take an “introductory” seminar, or read a guru’s website, is what is the subject persons BIAS?  If he’s selling you something, then there’s a very good chance his “pitch” is not truthful.  There are some very good localized mentors that hang around BP and contribute with excellent advice and information on forums, podcasts, and articles.  But something happens when and if they decide to 
go national”.  Those guys end up buying marketing programs from one of a few specialized real estate marketing organizations out of either Las Vegas or Salt Lake City; and the result is the cost of their programs goes from $3000 to $40,000, the quality of their information go from a 8 to a 4, and once you’ve entered their program all your contact is with an employee while the guru is out giving seminars, workshops, and making videos.