Does Spamming Twitter Improve SEO?

Maybe. But I still recommend against it.

From the ReadWriteWeb article by Sarah Perez:
A Dutch design and development firm Conceptables noticed some odd behavior regarding Google's use of the Twitter API during their development of Mopinion, an online feedback tool. It appears that simply repeating the same tweet over and over was having an impact on the actual Google search results.
 Each tweet contained a link, so the large number of tweets created a strong association between their webpage and the desired search term. Perez equivocates a bit about whether it actually works or was coincidental, but seems to grudgingly admit it works before concluding "the domain is a different database and may operate differently than, especially when it comes to social signals."

This sounds good in theory, but I have a practical and ethical objection to Twitter SEO spamming.

First, as Perez points out, it will most likely work differently on the main Google server. More importantly, this flaw having been exposed, I doubt Google's engineers will take it lightly. I expect the next revision to the search algorithm will address Twitter spam, and control for or even punish sites that engage in it.

Secondly, I am opposed to spamming of any kind on general principle. I even have reservations about direct mail, because too much of it is unsolicited and unwanted. Twitter spamming reeks of "black hat" technique; this type of behavior will clog Twitter, reducing the value of Twitter as a tool and the enjoyment of it as a social network.

Twitter can be an important SEO tool, but do it the right way. Publish consistent, useful information, and follow and retweet appropriately.