Here's some helpful advice from TSA:
'Footwear that screeners are less likely to suggest you remove includes:
"Beach" flip-flops
Thin-soled sandals (without metal)'
http://www.tsa.gov/public/interapp/e...orial_1050.xml
Probably best to avoid these: '...during a routine security check on January 31, authorities at Istanbul’s Ataturk Airport discovered electrical devices concealed inside the shoes of Gua Hongen, a Chinese national traveling through Istanbul from Beijing, China to Tripoli, Libya. The discovery of the device triggered a security alert at the airport.'
http://www.homelandsecurity.com/modu...index&view=535
But hopefully these will be deployed soon: '...the TSA is inviting companies to voluntarily participate in a test program to develop technologies for “Shoe Weapons Inspection Systems (SWIS) that can inspect footwear for weapons without passengers having to remove or divest them from their feet.”'
http://www.msnbc.msn.com/id/8899022/
I'm no cobbler but most decent pairs of shoes probably have a degree of metallic content and, despite the nuisance, there's good reason for the extra scrutiny. Definitely avoid the thicker soled jobs. A good pair of Hush Puppies work for me...!