i think Huobi, OKCoin have bots
Most exchanges offer an API, which software engineers can use to facilitate automated trading.
Willy/Markus bots sound like they were purposely programmed to maintain Mt Gox price index within tolerances. Then systematically make acquisitions which would only inflate
BTC price.
When the price stated shooting up last week, lot's of speculation appeared on this forum - with a lot of traders saying it's due to "Whale" action or market manipulation.
I'm not 100% sure similar bots aren't being employed at the Majors right now. But most believe recent activity to be legit.
I don't have a problem with the use of API's for conducting day trading margin buy/sell's. Just an issue with bots designed to manipulate the market.