Writing fake reviews.
Several years ago, I got offered, several times, the opportunity to write fake reviews for $20 a report but I chose not too.
One reason was my code of ethics told me it was wrong - damn those ethics they cost me a lot in the last decade - another reason is I thought if I got found to be writing them, the news would ruin my rep as a writer.
One interesting thought is I wonder how much I could have made over the years by writing fake reviews?
If I got the chance now, I doubt I would take a second thought as my rep is worthless and I make less than $5 a year from my e-books.