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<table cellpadding=3 cellspacing=0 border=0 height=40 width=100%><tr><td nowrap bgcolor=#ECF8FF height=40><font size=-1>Want more from Google? Try these <a href="/tour/services/query.html">expert search tips</a></font></td><td align=right valign=top bgcolor=#ECF8FF height=40><font size=-1 class=f>Shameless Self-Promotion</font></td></tr></table>
Why the shameless self promotion
The space might not be 'worthwhile' for a company, but if Google writes it down as an advertising expense I would imagine they would follow their own / and the FTC's guidelines on labeling it as advertising for themselves.
At least, that has always been my thinking on it...perhaps I'm wrong, though.
They also have a sense of humor...but, most of the site is serious. So they are probably just being funny in a tongue-in-cheek way.