tedster - 2:39 am on Jun 14, 2012 (gmt 0)
Even flat-out link exchanges can be OK - if they're not a big part of the total profile. The other scenarios you mention are also quite natural and not a problem.
Many webmasters have been freaking out about reciprocal links for far too long, IMO. The whole picture is more complex (and more balanced) than all this paranoia. It's a sign of not understanding the way the Google algo has evolved.
The way I see it, the main lesson is to find ways to earn other types of natural backlinks for your site.