A lot of elements were rushed. Some strange plot points, like how he invents the webshooters (hint: he does the equivalent of ordering them from ebay). They rushed other plot points (Uncle Ben's death) or they aborted them halfway through (Spider-Man is hunting down Uncle Ben's killer, gives up after a while).
He orders the webs, not the shooters. The webs are widely available, he just creates a mechanism that allows him to harness them in the way he wants. It makes a lot more sense than him coming up with a magical wonder-chemical that would probably take years and years of research to make, and it's better than organic shooters because it's another instance of solidifying Peter as A Smart Kid.
The problem is that creating a mechanism to shoot out the material in a straight line really isn't that complicated. I mean, I don't mind the idea of webshooters, but he ebay's the web material. What if Oscorp just decides to shut down production of it? Does he have any idea how to build his own? At least with the organic shooters you have justification, but really he's either gotta go all the way with the webshooters (build the mechanism AND the material) or not have them at all, because the current way just comes off as pretty weak.
--
TheRock ~ Slow dramatic zoom-pan. Doesn't phase the hooded man.
"You have issues." - MWC. Pot. Kettle.