I bought some platinum once or twice in EQ, after a a two year break. I wanted to get caught up with everyone and there was no way I was farming up enough for a decent mount anytime soon.

I never sold anything. I've thought of logging back in once more to try and sell my leftover cash, but I probably wouldn't get more than the cost of a month's play. I'd never sell a character because I never know if I'll want to play again. I've made a couple of returns to EQ over the course of its lifetime, as well as some other games.

Yup, I sold my WoW account to one of those online sites. They gave me $180 for it, seemed cool at the time, wasn't playing and I needed the cash.

I cannot tell a lie I have bought currency in several games in the past,

And to be honest i have no real issue with the notion of it "in principal".. whatever is said by companies "someone" is in game earning that cash legitemately, farming loot, selling crafted items/resources etc.. someone did spend the time and effort earning it and if they choose to get rid of it in a certain way so long as they're happy to do so i have no objections to occasionally paying such an individual for a financial boost when i have a specific need.
I mean they "could" choose to give it away to people and noone would have an issue, but if someone chooses to pay for it from someone then suddenly its not moral or fair play, pfft.. all just semantics.
Really its no different than say me payiing ncsoft for example to buy "thier" NCcoins for Exteel or buy RFOnline currency, these companies main gripe is because the currency isnt going in thier pockets, but they get my subscription fee, i buy thier expansions what more can they ask.

Though that said thier are other issues such as buying currency devaluing its percieved worth for instance (i.e if you have millions you have no qualms paying over the odds for things because you have lots of money), which in turn leads to people selling things for ridiculous sums, which can hurt game economies and those people who dont or would not buy currency, though i have always been careful to only pay sensible values in game for anything ive ever had with currency ive bought and Ive always made a point of selling anything mself for sensible prices because i wouldnt want to ever contribute to those kinds of circumstances. Also you tend to end up with gold sellers etc.. spamming like crazy with adverts, which is one sind of currency sellers I really detest.

I will say though, I wouldnt and haven't EVER bought game currency for just anything, i.e to "Twink" out, or to get ahead at the start of a game as i like to progress and explore myself.

If and when I do buy currency personally, it is almost always in order to help improve my crafting skills buying raw materials/resources, or buying that cool crafting recipe/schema that i couldnt otherwise afford, or more often than not in order to buy a mount or in game home (and pay its rent) as these things tend to be the real money pits in MMOs with most upkeep costs being only feasible for topped out level players more often than not and to a large extent the idea behind it being to force you to stay subscribed and continually playing one character in order to keep meetings the bills.. and that side of thing isnt fun for me its too much like real life hassles. So instead I buy a house pay off the rent for 3 years and then play or not without having the worry of my house and its contents etc..vanishing because i took a month off or wasnt logged on the day the rent expired, or spent two weeks playing an alt for a change etc.. etc..etc..

I would also never sell a character or account, or let anyone have access to my account details for any reason as thats just the sort of security risk that leads to identity theft etc...etc.. Nor would I ever pay for levelling services 9though god knows there has been a game or two i could probably use it lol).

I used to sell gold/items and property in Ultima On-line, was a good income for a few hours game play a day. It payed for 3 accounts, my internet connection, and monthly upgrades to my PC , and drinks down the pub most nights.
This was back when you payed to be connected to the internet by the minute (UK).