I would say "Insider Trading" in terms of the Bitcoin trading marketplace as it exists today exists with shady exchanges (whom are not subject to ANY "trading regulation", rule books, oversight, etc.) allowing market-makers to front-run orders, or worse yet, acting as market-makers themselves.

That being said, like currency trading, the only "insiders" are those in central government institution levels that are privy to interest-rate / policy decisions.

HFT is another animal, and a harder one to solve in the disparate market of Bitcoin "exchanges" (I wouldn't call them all real exchanges...) It's still very much impossible to do the kinds of HFT that is common in most existing traditional financial markets, due simply to a lack of infrastructure / capitol / specialized products (futures, options, lending, interest rates).

It (HFT, ULLT, DMA) will happened, but only once Bitcoin or some derivative there-of migrates into more established infrastructure.