Google Base good for linkbuilding?

Google Base is definitely a way to get some limited SEO exposure given that it's indexed quite thoroughly by Google, but given that listings expire in 30 days...I don't recommended it as a sustainable SEO strategy...unless you've got the time to keep reactivating listings and adding enough content around your temporary listings to maintain relevance.

I have heard some people recommending Base as an option. Wouldn't help a decent long term SEO campaign but if you're limited on indexing options it should be enough to get a site indexed.

I highly doubt you will get any seo value from them. Maybe good for traffic but no algorithmic benefits.

I suspect it's chicken & egg.  Duncan is probably right in suggesting the right Google Base spot might drive enough traffic to pick up a site.  As a direct cause-and-effect relationship, though, Brian is right that a Base advertisement by itself probably isn't enough to do it.

If I were starting a site selling a tangible product today, I would sign up for Google Checkout, post a spot in Google base, include an AdSense spot (where it made, um, sense), run a tiny AdWords campaign, submit a sitemap and link to a standalone Blogger account they host (You can always move it to your server and should).  Then I would submit to Yahoo paid.  Finally, I would make a small donation to a community college in exchange for a guaranteed link (not a no follow link). 

All are short-term things that can be quickly reversed.  All should result in being quickly indexed, especially if your content is remotely unique.

George that is a great checklist of things to do.

You should write a little bit more and expand that into an article.