It seems that alot of online businesses depend on Google for as much as 90% of their traffic. Is Google you main source of traffic? If not then who?
All over the place. The internet is huge man...I can't really pinpoint a source of traffic. Just make a good site, the traffic will come. Don't make a website for the sole purpose of slapping some copied and pasted content on it along with some ads. Make decent site, post decent content, be patient.
Google sends a lot of traffic my way but I try to mix it up as much as possible. I got wiped out by one of their massive updates a few years back and learned my lesson not to rely on search engine traffic too much as it sucks to be at the mercy of an algorithm.
Yes it does suck to be at the mercy of an algorythm. Just remember that it is Googles job to provide "relevant" content.