I haven't seen a consolidated thread on this topic, but I would like to start a thread that people post theirs and other's product warnings. The purpose of this thread is not to flame, but to inform and prevent future headaches for fellow forum members. Examples would include (but not limited to) shoddy craftsmanship or shady business practices.
I'll start with some posts I found around on this forum and others.
*warning* theft & fraud by rennen international
"Warning" Kranson Forged Lies and Bs - G35Driver
This Guy's Wheel Self-Destructed And The Company Who Made It Is Blaming Him