As the others have said/intimated... you should
ALWAYS investigate who you are linking to.
Especially the people that post here, and post just a url? or post NO url.. begging for trades.. Most of them I wouldn't go near if they were the last page on earth.
You can see what Google wants and doesnt want here -
http://www.google.com/webmasters/guidelines.html
* Avoid hidden text or hidden links.
One of the quickest and easiest things to do to detect possible shonky linking is do a 'cntrl-A' on the page they want you to link to... It highlights the whole page and will usually show you any hidden links at the bottom of the page.
IMO these Team not-so-Perfecto guys are the worse.. have a look back at any of their posts or URLS you will find the same stuff cross linked and hidden linked.
They have 100s of these domains -
http://pornstarspov.com/ - (if you dont see the hidden stuff as it loads , do a cntrl-A)
http://www.tokyodivas.com/ - same
etc.. etc..
In my opinion - who you
DON'T LINK TO is far more important than who you do!
DD