Do I need a screen protector for my new touch-screen smartphone?

• No, I hate screenprotectors
• Most of them really don't
• There are certainly bad ones, that are hard to apply or peel off easily, I've even had one that would blur the screen
• Only the ones that blur your screen ;-) They have a slightly matte finish so fingerprints won't be as obvious
• Yes, yes, and yes.
• I suggest you just replace them, they're not that expensive
• I believe it is all stupid...

They just make you feel better. The glass on the new iPhone is incredibly difficult to scratch, and even the older ones hardly scratch at all. I suggest you stop caring so much about a little scratch, the device is supposed to be used. You'll hardly notice it if there even ARE tiny scratches.

If you want to protect it, what you really need to worry about is the thing breaking after you drop it, try a protective case instead. :-)

I'm afraid I'm going to have to disagree with sebastiaan on almost all points, just to complete the spectrum :)

• Yes, I've almost always had a screen protector on my smartphone.
• Sometimes the screen protector interferes with the touch screen. Depends on the quality of the touch screen, and the screen protector but in most cases you might notice a slight change in responsiveness. Are all screen protectors created equal? Are there "good" ones and "bad" ones?
• Very yes. Some are just clear stickers, others (like my favorites Invisible Shield) are the same material used to keep dust from messing up helicopter blades)
• Sometimes. This goes along with the quality of the screen protector. But in most cases there will be less fingerprint smudging.
• They can get dirty if they're low quality, or not applied carefully. Usually lint or dirt will get its way into the edges and start to peel it off. How well this works depends on the screen protector and the surface you apply it to. But if you're just covering the screen you should be fine.
• Usually just wiping it on my pants will get rid of most day to day dirt on it. The big advantage is that if you get something stuck on it, you can scratch it off without worrying about your screen!
• I had a full body protector on a blackberry tour for nearly a year before it started to peel off, and it really only started to come off on the curved surfaces. I pulled off alot of the body protector, but left the screen protector on, and it's still going strong.
• The invisible shield (I swear I don't work for them) can be bought as a full body kit, considering the shape and material of the iPhone4 I would say it's not stupid. You want to protect the phone to keep it looking nice, then treat the front like the back, since they're essentially the same thing.

I did not use one for my iPhone as the screen is glass and hard to scratch.

I am using one for my Nexus One because the screen is plastic and probably easy to scratch. Since putting the screen protector on I have stopped using the case. I am using the Invisible Shield that Alex likes.

I would have said no, you don't need a screen protector on your phone. I've never used one on the iPhone, Palm Treo, Nintendo DS, etc.

Then my wife dropped her iPhone and the screen cracked. We're going to get her a screen protector now, so she can keep using the phone without worrying about it scratching her.

I see that you have marked as an accepted answer. However, there is another proof that screen protectors these days have more essentials than Corning Gorilla Glass that protects well from scratches. As I took some few research, I found some useful benefits why people prefer screen protectors in the following:

• Prevents heavy scratches
• Easier to clean fingerprints
• Can resist screen breakage from an impact

Not all the times that glass technology always invulnerable to scratches. When it say "scratch resistant" it means no scratches in a certain number of times. Also, like other usual glasses do, it breaks like fragile glass when it falls. You may check the Upgrade Your Life blog post about useful truth about screen protectors, including some video and descriptions and find out what I really mean.