We use Google Analytics to track metrics on our site. I'm doing search engine marketing with both Google and Yahoo. There is a HUGE difference in the visits we "see" on our site vs. what Google and Yahoo say they're sending us. I know there's going to be a difference always for many reasons. GA isn't perfect, bots and spiders, people bouncing before the full page loads, etc. But that shouldn't account for too much more than 10% from what I'm told. I'm seeing a difference of 2 to 3x. Both Yahoo and Google looked and said our tracking is set up properly, yes that's a way bigger variance than normal, we don't know why.
Has anyone else encountered this problem? Did you find a resolution or way to mitigate it?