It's more than likely different sets of "whales" or people with generally large amounts of BTC, that are interested in Darkcoin and believe that it can reach much higher prices. After all, we are "early" on in Darkcoin, huge interest really began happening about a week ago, and the price could reach much much higher than this.
If I was a Bitcoin whale, I'd constantly be on the paranoid lookout for the nearest contender and invest at least 5-10% in it as a hedge.
Until a couple of months ago I thought it was guaranteed to be Peercoin. I still actually think Peercoin's got a huge future, but I'm not invested at the moment because there was so much else coming on the scene.
DRK's an obvious strategic threat due to a genuine commercial advantage - whether perceived or real. So I can see it from that point of view.
