Update (Nov. 2015)
Vibram, an Italian footwear manufacturer and maker of FiveFingers Shoes, has settled a class action suit brought against them for false and misleading advertising. In the settlement Vibram must cease advertising their products as offering safety benefits nor providing an environment similar to being barefoot. They were also required to make reimbursement to customers. 

Update (October, 2011) Injuries with minimal shoes
As predicted in the original critique posted 18 months earlier, practitioners of sports medicine are now frequently seeing patients with injuries associated with running with minimalist shoes (now often called "barefoot shoes"), soon after switching from more typical running shoes. Some barefoot runners who are tempted by advertising to try these shoes report pain at the metatarsals when they use them. This pain ends when they return to barefoot running.

There can be a delay of months to greater than a year between submission and publication of reports in medical journals, which indicates that reports now appearing in medical journals about injuries associated with "minimalist" ("barefoot") shoes started to occur soon after they were introduced. In one recent report two runners sustained metatarsal fractures when they commenced using minimal shoes. More reports will surely follow.

Zipfel & Berger reported significantly greater damage at the metatarsal-phalangeal joints in a shod population compared to an exclusively barefoot one despite greater weight-bearing time with the barefoot cohort.  This indicates that injuries associated with minimalist shoes resemble those seen with more typical running shoes. Also, running with minimalist shoes does not resemble barefoot running. 

The incidence of these injuries in users of minimal shoes appears extremely high by initial reports - more than is seen shod runners. This can be explained by proven mechanisms. When new products are advertised to protect via a mechanism that the user can not sense, a false sense of security is elicited which has been shown to result in higher impact. Minimal shoes are deceptively advertised as having the protective advantages of the bare foot during locomotion without a datum to support this claim. This gives users a false sense of security which could account for injuries. Furthermore, minimal shoes resemble all other footwear with regard to the level of protective plantar sensations produced during locomotion that initiate protective responses. They moderate localized plantar deformations and reduce plantar shear relative to equivalent levels associated which barefoot locomotion. This accounts for attenuation of the behavioral response which protects the unshod individual.

Giulliani j, Masini B, Alitz C, Owens BD. Barefoot-simulating footwear associated with metatarsal stress injury in 2 runners Orthopedics, 2011 jul7;34(7):e320-3

Robbins S, Waked E. Hazard of deceptive advertising of athletic footwear. Br J Sports Med. 1997 December; 31(4): 299–303.

Robbins S, Gouw GJ, McClaran J, Waked E. Protective sensation of the plantar aspect of the foot. Foot Ankle. 1993 Jul-Aug;14(6):347-52.
(Original posting - February 2010)
The "minimalist shoe", and other products that infer barefoot simulation, resemble shoes that preceded them in terms of plantar sensory feedback and mechanical properties of sole materials. The "minimalist shoe", and other products that infer barefoot simulation, resemble shoes that preceded them in terms of plantar sensory feedback and mechanical properties of sole materials.
They do not simulate the bare foot condition, and to suggest so is misleading. They possess highly resilient materials in their soles, which destabilizes users, resulting in amplified impact. 
Manufacturers of these shoes have provided no data indicating that they offer advantages in terms of impact control when compared to more traditional athletic shoes.
If the consumer considers the modern running shoe to be hazardous and frets about being misled by shoe manufacturers, they risk being similarly misled by these products.
A detailed critique is available on a separate web page.
Links to relevant published reports: 1992-1.pdf  1994-1.pdf  1995-1.pdf