I haven't followed this particular story all that well, but if nothing else this was the largest number of transactions that can be made in a 10 minute window of time. I believe this might be the first time that limit had been hit, but if bitcoin keeps growing it won't be the last, especially if the block size isn't increased.

The reason that this is a problem is that the "confirmation time" has always been a point of contention for bitcoin. Currently, you have to wait up to 10 minutes for a transfer of bitcoin to be finalized. After that first confirmation you're fairly safe, although some extremely complicated and expensive to pull of tricks could still be played. Before it, however, there is much more that can be done to reverse the transfer.

The problem is that in order to hit the max there are some transactions that didn't make it in, and will take an additional 10 minutes to confirm. If we get to a point where even half the blocks are full the time for transactions to confirm will be almost unusable (in my opinion).

All the miners(computers) have to calculate all the different hash codes , and why is such a big transaction bad? Because it wasn`t really one big transaction, they were spamming the bitcoins around the world with thousands of transactions so there is so much traffic the miners get slower and slower with the calculations.Why was an atack? A simple comparison, if there is a limited amount of water in a town and one of your neighbours pumps all the water in his (swimming)pool no one else get enough water (shower,toilet,cooking, etc...) I think everyone of us would take the water back...?