LinkEx trades can penalize your site
 

I just read on gogle webmaster forum that trades using LinkEx can lower or even penalize your site by google.
I remember that i did trade with one of my mainstream blog using this script and after some time PR dropped from 4 to 2 but can't tell if that was because of this trade or something else.

Anyone else used LinkEx trade and notice something?

You can use LinkEx but when you output the links, choose to not output the text that says the following:

That piece of text will definitely get you penalized as it clues Google that you are trading links using a trade script.