Coop, LV and ReceiveLinks

[stoli_sambuca]

I have been reading about Coop, LV and ReceiveLinks, and quite a few people claim that they lost rankings because they used Coop, LV, ReceiveLinks or any combination of these three.  Is this a legitimate claim or not?  Also are these link networks helpful, harmful or neither?  If neither, then is there so called "right way" to use these networks such as

- Limit number of links displayed on each page
- Not using your main site(s) to display links

...?