This news reveals then that they lied. It was stated repeatedly in #mtred on freenode -- which is where I started lurking when my rig was unable to connect to the pool -- that they brought the pool down in reaction to a very strong DDoS, and that they were rewriting the payment algorithm in the interim.

That being said, I'm not sure why you think they wouldn't be subject -- along with every piece of infrastructure in the bitcoin food chain -- to very large DDoS attacks. The currency manipulators are here to stay. To think otherwise is foolish and misguided, or hopeful beyond reason.

The fact that every bit of infrastructure is being "attacked" at once suggests that it is not a DDoS attack to me.

If the price starts going down, everyone will rush to their favorite bitcoin related site to see what is going on, even if they are not planning on panic selling. Would you say you have checked bitcoin related sites 5 times more than usual today? 10 times?

If the regular users of a site all decide to use it five to ten times more than usual, it is very likely to cause some slowdown.

On the other hand, if a single bitcoin related site was experiencing problems, that is when I suspect a targeted attack.

Lastly, the only thing that mtgox announcing that they have been DDoSed in the past tells us is that they are willing to announce the fact that they are being DDoSed. This would seem to make it less likely that they are being DDoSed in the absence of such an announcement.