This is very true. Guidelines talk of not doing things "excessively" but no-one knows what excessive is.
In fact, if anything the recommendations have got more vague. For example, back in 2009 Matt Cutts said that Google's recommendation was to “Keep the links on a given page to a reasonable number (fewer than 100).” (http://www.mattcutts.com/blog/how-many-links-per-page/
) and he actually linked that statement to Webmaster guidelines. But if you go there (http://support.google.com/webmasters...n&answer=35769
) the first part of that statement is still shown but the "(fewer than 100)" has been dropped.
So all we are left with now is guessing what is "reasonable".