The argument for DRK being a scam is the instamine argument. Because the formula that specifies the block reward is a function of the difficulty (the higher the diff, the lower the reward), and the difficulty being low in the beginning, a large amount of coins were mined within the first day or two before the difficulty caught up with the hashrate. It was an unfortunate incident as the instamine accusations have been following DRK since then.
The developer (eduffield) even suggested and started a poll whether an "airdrop" should be issued that would disperse 2 million coins to everyone in order to dilute the effect of the first days' mining. This imo shows that the instamine was not intentional by the devs. The community didn't think such an airdrop would make any sense as the instamined coins were already long gone and distributed in the first months when the coin's value was very low. Can't say everyone who mined in the beginning sold though, as there were a lot of people mining. The airdrop idea was then soon abandoned.
And funny enough, no one gave a shit about any instamine when the value was low, everyone could've bought a large amount very cheap. The crying started only after the price started to rise and people thought they missed the train.
Here is a post about
The Birth of Darkcoin by the dev.
It was January 18, 2014 and I had everything ready or so I thought. I announced the launch of Darkcoin (XCoin at the time) on BitcoinTalk. We launched later and immediately got stuck on block 42, I was new to the Bitcoin codebase and wasn’t sure what I missed so I announced we’d relaunch later.
When we relaunched we had a rush of miners join causing a huge spike of coin production without it being able to adjust the difficulty quick enough, we just ended up spilling out coins. Retargeting happened every 576 blocks and could only increase the difficulty by four times, so it took about six retargets to get to a difficulty that was near 2.5 minutes per block.
Later on, after the difficulty evened out we realized that there was a serious problem with the block reward calculation. You can see people discussing the problems here:
https://bitcointalk.org/index.php?topic=421615.120I soon fixed this issue at block 4500, but none of us realized the amount of coins that had been issued at the time. At that point we didn’t even have a block explorer yet.