From snopes: (we have an ex-marine at work showed us that picture, we thought his stories were a bit much so we did some checking)
According to most spider experts, these claims are all false. Camel spiders (so named because, like camels, they can be found in sandy desert regions) grow to be moderately large (about a 5" leg span), but nowhere near as large as dinner plates; they can move very quickly in comparison to other arthropods (a top speed of maybe 10 MPH), but nothing close 25 MPH; they make no noise; and they capture prey without the use of either venom or anesthetic. Camel spiders rely on speed, stealth, and the (non-venomous) bite of powerful jaws to feed on small prey such as other arthropods (e.g., scorpions, crickets, pillbugs), lizards, and possibly mice or birds. They use only three pairs of legs in running; the frontmost pair (called pedipalpa) is held aloft and used in a similar manner to the antennae of insects. Camel spiders shun the sun and generally hide during the day, coming out at night to do their hunting.
Although whatever is depicted in the photograph above appears to be far too large for camel spiders, the creatures might just look unusually large because they were held close to the camera, creating an illusion of exaggerated size. However, since we don't know the source of the picture, we can't yet rule out the possibility that some other misdirection was involved (e.g., digital manipulation, a misdescription of what the photograph depicts, some soldiers goofing around with plastic figures or something else spider-shaped, etc.).