Some of the reasons those coins didn't succeed:
1. Some pre-mine or "test" mining.
2. Some difficulty 0 and had a lot of hardware ready with their insiders
3. Some difficulty 0 and get over-mined since the very beginning before nodes are well distributed
4. Some only got mined at the beginning when it was easy and then they stopped
Why is digitalcoin different?
1. No pre-mine or any semblance of it.
2. Number 1 again.
3. digitalcoin had very low rewards at the beginning so coins didn't begin to be distributed in quantity until many people could participate
4. It is more profitable to stay with digitalcoin due to the nature of the reward system
DigitalCoin won't succeed for a different reason. The chosen block time is actually too short. I write about why that's a bad thing here:
https://bitcointalk.org/index.php?topic=211535.0I read that. Good thoughts. One of the developers who took part in this project did take care of that for us. Check the pool rates for the orphan rates and efficiency.