So, if companies like Sony, MS and Steam can't defend against a targeted DDOS attack, please in all your wisdom, explain how you successfully have done this. Heaven knows, the entire world will be happy.
All of those companies were caught with their pants down.
So not really sure why you hold them up as a good example...
Typically DDOS attacks originate from a single country which is relatively easy to block.
Black hole for a given CIDR and IPs would be the strategy.
To give you an example:
Microsoft's failure is especially embarrassing for them.
They run Azure and this app was almost certainly hosted on Azure.
Clouds like Azure operate with a edge router where traffic enters into the data center.
The fact that Azure didn't go down during this DDOS means that the edge routers weren't overloaded.
They pushed traffic on to the service that went down.
In this case you would black hole on your edge routers.
For something like Cool Ideas, it would depend on their network topology.
If their entire network is dependent on a single exit node in Cape Town, then they likely will be unable to weather a serious DDOS attempt effectively.
I'm hoping they have at least SOME control of exit points on various parts of the network where the traffic can be black holed.