Are there any guidelines on how
tags should ideally look like? Are they links, buttons, or visual "tags" with a link?
I personally find tags that mimic a physical tag or strip of tape appealing, but oftentimes tag listings also have the tags as buttons or simply as links. See the following examples:
Illustration 1: Tags as buttons, as used on https://stackoverflow.com/
Illustration 2: Tags as links, image from http://productblogarchive.37signals.com/products/2009/07/new-in-highrise-improved-tags-presentation.html
Illustration 3: Tags mimicing a physical tag, button like, as used on http://delicious.com
Now I found a couple of questions on UX.SE about links and buttons, but none specific to tags. The best answer in the question button-vs-link states:
Rule of thumb: a link takes you to other place, a button makes something.
This would mean tags should be links rather than buttons, as they usually bring up a collection of items tagged with given word. Or is the visual metaphor of a button-like tag more important than the implicated action?
While I couldn't right away find an example of tags that look like buttons that have a link as label, I certainly can recall having seen those. Thus this question is also of interest, but not specific to tags, and would conclude to make the tags buttons.
One point that would advocate for more soft tag buttons is answered in this question about round buttons, but obviously the visual imitation of a physical tag takes this one step further.
Are links acceptable in tag collections or are tag buttons or even visual labels more advisable, and with what reasoning?