netmeg - 2:11 pm on Oct 9, 2013 (gmt 0)
Seriously, what's to keep anyone making related site after related site and linking it to their main site?
Lots of people do that, and Google has gotten better at detecting when it makes sense to do that and when it doesn't. It's not as easy as "always do this" or "never do that."
In my case, if I put a link one one of my sites to one of my other sites, it's because I think the users of the first site would genuinely be interested in the content of the second site. (And my stats bear that out) If I don't think they'd be interested, if I would only be putting the link there for the sake of having the link there, then I don't nofollow it - I don't put it there in the first place.
It's a nuanced approach, and if you're not sure and you're feeling a little paranoid about it, then just don't place the link. If you think your users will genuinely find it a useful resource (whether it's your own site or not, and whether it's directly related or not) then put a link there and don't put nofollow on it. And don't get crazy with the anchor text either - just use the name of the site.
But if you want a straight out formula for when you link and when you don't link, you'll have to keep waiting because there isn't one.
I agree with nutmug
You of all people should know better. If I had a link to you, I'd nofollow it for that.