I'm a Professor at Lewis and Clark College in Portland, Oregon. I study spiders and am mostly inspired by understanding how biological diversity comes about through evolution. When it comes to spiders, I specifically focus on the venom. Every individual species has a cocktail of chemicals in its venom, and the composition of that is different across different species. A number of things influence patterns of diversity in venom chemistry, such as prey capture (what they're eating), who they're closely related to and what they've been historically stuck with, before evolution changes and modifies that.
In terms of the movie Spider-Man, the chances of turning into a spider from a spider bite is non-existent. I'm afraid to say, even taking on spider powers from a spider bite is impossible. I just saw Spider-Man 3, and they flashed to the spider that originally bit Peter Parker. I didn't look closely, but it looked like a hybrid spider, a cross between a false Black Widow or a Button Spider, which is a relative of the Black Widow. The eyes look like a Wolf Spider, but the body doesn't, so it's some kind of computerized composite of two spiders, painted flashy red and blue.
The whole spider-silk thing gets really played up in Spider-Man. I think it's a fantastic advertisement; spiders' silk and web-making skills are so unique, that I think it's appropriate to model a superhero cartoon character after a spider.
While spiders' silk is awfully cool, in actuality, it doesn't fly out of the body; it's drawn out. For example, if the spider is walking along, it will start a silk line from the spinnerets on the back of its body to a branch or a wall.



