That doesn't work in all cases. If you can't distinguish between good and bad traffic or if it isn't specifically targeting an entity it becomes much more difficult to handle.
It also depends on the ingenuity of the DDoS attack, none of which are known to the public so you can't really say anything sensible about it.
If the anti-DDoS mitigating tools they are using aren't working nor is using other services like Prolexic that's usually hint enough that this isn't particularly common or easily filtered out.
You can gripe on all the companies and tools if you will but a good DDoS is quite a bit more complex than 'just filter away the bad crap'.
(4) Some things in life can never be fully appreciated nor
understood unless experienced firsthand. Some things in
networking can never be fully understood by someone who neither
builds commercial networking equipment nor runs an operational
network.
