The concept of the "SEO Footer" is a pretty lame and old technique, but not all SEO Footers are created equal.
The mint.com footer, many tiny links, almost the same color as the template, is lame and verging on grey hat.
The arstechnica footer is totally logical / ethical / usable / whatever.
You can tell that mint.com is pretty aggressively SEO'd - 90 character, no stop-word titles, perfect canonicalization, perfect image alts.
They're probably primarily doing the SEO footer for site-wide keyword rich internal anchor text.
Maybe they're also worried that search engines wont crawl the drop-down menus.