I've seen a few posts where people claim they have identified bots manipulating Bitcoin prices... I haven't investigated that in detail and I think what one calls "manipulation" is something another will call "finding equilibrium price".
So my personal conclusion is that I don't give it a shit as it doesn't matter and it's actually a good thing to see some people actually willing to put their money where their mouth is. A lot of people seem to just drown this forum in useless noise and pump and dump / FUD schemes... Speaking with your money is usually much more effective than speaking with your words.
What I noticed however is that there are bots on MtGox and Tradehill that are incredibly badly designed and that are easily manipulated / taken advantage of.
Over the last month, I was able to bring prices down across the market at least twice, and brought them up once, (by up to 5%...) without even actually making a single transaction, by taking advantage of theses bots. (basically every time I tried... it was fun!).
Pretty simple how you do it... Take a wide spread on Tradehill, put a buy order for like 0.1 bitcoin at 0.0001 or something above the current bid price (if you want to bring prices down, do a sell order) and you will see almost instantly a bot undercutting you by a little bit. Cancel your order. Repeat. Do it fast enough and you can bring the price up or down
Now bot writers need to take in account the market liquidity in order to not be fooled by such simple techniques.
Shameless plug here : I've been writing automated trading systems for the stock market and forex for about 8 years, and I'd be more than happy to provide automated trading programming / consulting services to large miners, large volume merchants or very early investors who are sitting on large quantities of bitcoins (50k or more, please don't waste my time if you have 10 bitcoins to trade...).
I'm not looking for compensation in the short term for my work, but rather for a long term partner (or partners) that has access to a lot of bitcoins or a regular bitcoin flow in order to set up a good market making platform. I am also hoping to be able to learn a lot on the bitcoin economy from you, so I'd rather work with someone who has been around for a while and who has a solid background in technology and / or economics.
I have several trading models and market making algorithms that I've been trading very successfully on Forex and on the stock market for years, that could easily and quickly be adapted to operate on bitcoin exchanges. I also have significant capital (in USD and CAD) to invest, as well as pretty good connections in the technical and financial spheres that we can bring on board in due time if needed.
Please send me a PM if this is something you would be interested in. Please make sure you fit the profile of partner I'm looking for and don't take it personal if I ask a lot of questions and / or want to move slowly / for the long term.