cnvi - 9:45 pm on May 3, 2011 (gmt 0)
do you know something we don't, or is this just another guess?
The answer to everything you want to know is in your server log files.
In a given month, when I see 25,000 visits from google for my primary keywords showing an average user session time of 19 seconds and few sales, I know "its not just another guess".
When I see 100 hits from my relevant link partners showing an average user session time of five+ minutes and good conversions to sale, that tells me everything I need to know.
But if you shun relevant link partners because of whatever paranoia you have read on the topic, its going to be harder for you to compare traffic from search engines vs. relevant partners.