I don't remember exactly when I bought mine but I did it to support the forum, not for the added privileges.  I actually turned it off for some time because I thought it looked "tacky" with my lower rank.  That was probably after theymos implemented the 1 merit requirement for Jr. Member rank.  There was a rash of shit-posting newbies buying copper membership at the time so they could post photos.

Now that I've "grown up" I don't care if it looks tacky, and I'm not sure it does.  Some months ago I turned it back on because, I don't know, it has a bit flair to it?  No particular reason, really.  I know it creates a bit of snag for those who like to scrape the forum for data, sorry about that.