Whitey - 11:31 pm on Feb 25, 2013 (gmt 0)
Anything scaled seems suspicious and might be flagged for editorial review and subsequent interpretations for applied penalty intervention.
Anything with a pattern seems algorithmically traceable if on any scale. Anchor text, tools , networks , spikes etc
Anything associated with high quality and reputation receives merit. It doesn't always require a link to gain a phrase, although clearly it may help.
Small scale digretions would seem to me to be below the radar thresholds - but since there is little scale of return few would do it and why would Google be bothered to police it.
I get the feeling that Google's Penguin update simply was a case of Google throwing it's hands in the air and saying, we can't differentiate paid links effectively, or, it's too costly to monitor. So let's throw anything relying on links within these patterns out the door and put focus mostly into brand and quality signals.
That said, investment in any form of external linking would seem to be unwise, unless it is redefined in the context of brand building and freely given editorial links that show natural phrases, or about a feature or benefit that is unique and for that you don't need large scale linking.
The days of having the most links to gain a phrase in competitive markets that scale are long gone.
I think investment in brand building that shows online, in this context, is better. Not volume, but quality. Links might come as a consequence of that, but if what you offer is unique , attributions by association regardless of linking will play it's part.
Trying to work out what's in, and what's not in terms of Google's acceptance is really on the edge of risk. And if it's not clear, steer clear IMO.
So the key, in my view is attributing relationships of quality. Inducements may play a small part, but I'd say it's tricky territory, and not necessary where quality is involved.