I just don't get why Googles results are so unpredictable. The last weeks I have had from 1,500 unique visitors to 7,000 unique visitors a day to one of my sites. Today it seems to be more like 1,500 visitors than 7,000 from what I can see in my stats. Something weird is going on with Google as usual and the thing I don get is why does it fluctuate this much from day to day. You would think that a lot of people would be using the same keywords to find the site but that changes too. One day I see some keywords and the next day they are gone and people have been using other keywords to find the site. To me it doesn't make any sense. What are they doing, how are they doing it and why are they doing it? I could understand if I changed a lot but I don't Keeping the same meta tags, almost same content except for new ads people post, so it can't be me do9ing something "wrong".....
Maybe you are coming out of the sandbox or about to get a penalty. Without analysing the keywords, rankings and traffic its hard to say.