Saul Bass is easily one of the great designers in graphic design history, known both for his pioneering film titles as well as for his logo design. I ran across a great blog post today by Christian Annyas showing how companies have changed (to put it probably too politely) some of his work since it was designed. (In the interest of full credit and disclosure, I found the post from a tweet by @trufcreative, which led me to a blog post by @LogoDesignLove, which led me to Christian's post.) I thought these deserved special attention as great examples of how "improvements" to a logo often end up being much weaker design that dilutes the strength of a brand. These "improved" logos fall victim to treatments that date themselves. While you could argue that these type of treatments might be appropriate in packaging or other materials that work with and around a logo, the logo itself should be clean and strong enough to be timeless. Christian's post shows many other Bass logos, and takes another angle on timelessness by noting the lifespan of them, the average of the examples he shows is 34 years. Lets hope the surviving ones live a lot longer without falling victim to shortsighted attempts to be trendy.
[apologies for blog posts before 11/2008 that are not yet updated to format]