@Gentso- do you believe there is any such thing as a perfectly accurate price? What's the spread at btc38? 1%? 0.5%? Which price is the price you think is "correct?" The bid or ask? The price of the last trade? I think you'll agree with me that none of those are quite right; you'd almost always be more interested in something between the bid and ask. So what do you pick? The average? A recent moving average of market prices? Those sound better, but they're still only estimates. Maybe I'm being long-winded, but I'm trying to make the point that there isn't ever 1 price and the best you can ever do is estimate it. So adding in 0.2% noise will still give an accurate price feed, especially if everybody is doing it and all the noise averages out.
@Xeroc, I haven't actually designed a manipulation algorithm to exploit feed price prediction, but isn't it obvious that a noisy feed would be better than a predictable one? I'm working from this principle: if I can execute trades on btc38 and predict exactly what that will do to the price feed, then I can make money moving the price feed around. Probably a fraction of a percent per trade, but the fact is I'll be taking money from the system without providing any benefit. Doesn't that sound like something we should try to prevent?