I get emails saying they have added my link to somewhere and they are asking if I will link to another site and not the one linking to me, how crappy is that?
could be a con but it is also called no reciprocal linking if you get a link from someone and they ask for a link back google recognises this and it is called a reciprocal link if you get a link from one of their sites and they get a link to another of their sites from yours then you both have a one way link. this counts for a lot more in googles eyes so make sure they link to you and link to wherever they ask you to
I think it's grey hat, as it's slightly less then ethical ... though if the sites in question (all three) are related, it should be OK, as there should never be anything wrong with linking to related sites.
i dont know if this falls under grey hat or white hat it is basically three way linking something that no doubt happens naturally all the time. i dont know google or yahoo's stance on it to be honest but it is something i will look into but essentially there is no problem with saying Hey can you link to me? sure will you link to this site in return? yeah sure whats wrong with that? other than the punctuation