I have 10 sites. From 29-30 november to today I have 2-3 unique visitors for each site. Before this time I have 100-200 for each site. What's happen? Did Nobody collide with similar? Filter? New Algorithm? Or What?
My SE traffic has been going up and down like a yo-yo. Currently it is down, but I am hopeful it will come back again and stay.
You will need an analysis, background check on the time your traffic is high. things to consider like - keyword ranking? - pages drop? - banned? - do you build links? and more....
Link exchange does not guarantee web traffic. The best visitors come from search engine. Therefore, SEO is the key here. Buying links may boost the page rank of your site but most of the time, this is not the effective way to build up good traffic. Just my $0.02