All of these anecdotal postings are interesting, but don't really provide solid information regarding the risk of hawks to domestic cats. Hopefully the following information from http://www.hawksaloft.org/faq.html
"Can a raptor carry away/eat my pet?
Raptors hunt a variety of prey, including rodents, birds, rabbits, snakes, and insects. And yes, large raptors, such as Red-tailed Hawks and Great Horned Owls, can indeed kill a small pet. We have received dozens of inquiries about 6-pound dogs, 10 pound dogs, 10½ pound dogs, etc., all the way up to a 60 pound dog. There is no specific cut-off weight at which your pet’s safety is guaranteed. If the size of your dog or cat is similar to or not much larger than naturally occurring raptor prey, there is a risk.
If you are concerned about your dog or cat, the best advice we can give you is to keep your pet indoors or supervise them closely outdoors. There are several good reasons to keep cats indoors. Outdoor cats face considerable danger from vehicle traffic, as well as harassment from larger animals, such as dogs and coyotes. We think these threats are responsible for a much greater share of mortality than raptors. In addition, outdoor cats are responsible for killing millions of wild birds every year. Turnabout may not seem fair play when it comes to a raptor threatening our beloved cat, but by allowing our cats to roam free, we are exposing them to this uncommon danger.
When it comes to dogs, we know it is often necessary to keep them outdoors. If you live in an area with a substantial population of large hawks and owls, perhaps you can protect your dog by providing an outdoor shelter or covered run.
As pet-owners ourselves, we at Hawks Aloft share your concern for the safety of your pet. But while keeping your pets secure, we encourage you to take an extra moment and appreciate the remarkable wildlife that also shares your space. Like our faithful dogs and cuddly cats, backyard birds and wildlife can greatly enrich our lives. "