I've also heard a few rumors abou that. But Michael Schmitt, software engineer at Google and Speaker at SES in Munich, agreed that it wouldn't really make sense. Lots of european companies have their servers in the US due to lower costs for webspace and/or bandwith.
I work for a webhosting company and I can tell you that plan of attack would make no sense whatsoever. We have thousands of European customers who sell small business European products from our US servers to Europeans only. Not to mention hundreds of other countries like Australia or Japan. On the flip side, prior to working for my current company, I used to personally host a US based small business website on a European webhost. There's no way that server location is a practical way to raise or lower SERP position.