Here's how the program works: Players earn Hero Coins whenever they make qualifying purchases from the L2 Store or the L2 Galleria, with coins awarded retroactively for all purchases since November 30th, 2011. Sounds decent so far, right? But this is where the program loses its appeal for some players.
Hero Coins are not account-wide; they're bound to whichever character received the purchased item. On top of that, all Hero Coins expire at the end of every calendar year at 3:01 a.m. EST January 1st, so players can't accumulate them until they can make a decent purchase. And accumulate they must: There are items in the rewards program that equate to over $35K, but can be found on the black market for approximately $2K. For really big spenders, the top item converts to spending over $200K in cash in the store -- in a single year.
[Thanks to Ville for the tip!]