- The market doesn't care about patents. Whether your product is good or bad a patent makes absolutely no difference to a customer.
- Competitors care very little about patents. They know the cost of patent litigation, and that you probably can't afford it. Even if you could they would probably be able to strike a deal.
- Investors, on the other hand, do care about patents. The thinking seems to go along the lones of I have no idea which company to invest in, but the ones that have a patent must be the smart ones. So those are the ones I'll invest in. - This is from Denmark, and may be different depending on your meatspace coordinates.
- Patents take time and focus. Patenting takes the focus off your product and selling it, and patents don't get you customers.
I would say that if you're gunning for investors get a patent, if you're not don't.
Hope it helps.
Edit: bonusinfo: If you have to go out and get a job at some point later in life a patent definitely helps. Employers are pretty impressed when you can say that you're so smart that you've taken out a patent...