Peeples and Bankscottage have already summed it up!
There are many threads on the forum about this.
Google introduced an EMD (exact match domain) update on 27th September and everybody's traffic nose dived. Most webmasters were rather bemused by this as non-emd's were hit also.
6 days later, Matt Cutts belatedly announced that a Panda update had also been implemented. Some are referring to this as Panda 20 as it is the 20th update.
If that wasn't enough, they also running another Penguin update.
In addition to this, Hubages staff have been making a number of 'improvements' to the site. Not all site members share the staff's enthusiasm that this is having a positive influence on site traffic.
In fairness, with so many changes, it is going to be difficult to pinpoint specific problems until the dust has settled.
Nonetheless, the forum is the place to read more about this.