I sold 500,000 DGB during the pump yesterday and am buying back today and will make around 210,000 DGB, not bad for a few mins work

Sell high, buy low and all that.
You earned that at the cost of the Demand's price confidence. If you hadnt sold that amount.. and probably would have held on to it... There's a chance that the exchange (buyying and selling) would keep on going. Thereby giving you 500K dgb close to your total DGB now (in value).
I would prefer a healthier supply/demand without that sort of speculation

Then again, its always about luck here and there. Ah well,..
This is true.
It's a tough call because I'm sure we all mine & would like to realize a bit of cash to pay for electricity etc, but selling large amounts is indeed detrimental to a big rise back to the 300 or so we saw last month. There was obviously a concerted effort to do so last night at least twice, but because it was quickly pushed back down below 100 confidence fell right away & now we're back where we started.
I said it before, but I really mean it that there is no difference between multi pools dumping & us holders dumping. The coin will never rise as long as people only view Digibyte as a money making-tool rather than as money (as grynca said just above)
I was looking at mintpal yesterday when pump&dump happened ( by coincidence, i dont look there all the time ;] ). Because it is such a small market it took about 6BTC of buy orders to launch the price up to 190 satoshi. But then there was no sell wall to keep the price up so it fell back down. A little later there was the error with coinmarketcap showing some crazy buggy figures so price went up a little again.
Again in such a small market as mintpal nearly everyone with a few BTC can create large pump and nearly everyone with enough DGB can create large dump.
But this is not what this coin should be about, we should try to use the coin as it is, not marketing it for another currency.