Owners of the iPhone 4 who purchased it on or shortly after launch date will have their factory warranties expire soon, as the standard warranties on most Apple products—the iPhone included—last for about a year before they expire. iPhone 4 owners can check the status of their warranty and when it is due to expire by entering the iPhone’s serial number here.
The expiration date of an iPhone 4 owner’s warranty is also the last day one will be able to purchase AppleCare for it, which extends the warranty to two years instead of one and includes unlimited phone support for $69 USD.
If you happen to be an early iPhone 4 adopter and find your warranty to be of importance to you, you should probably purchase AppleCare now before it is too late. AppleCare can be purchased online directly from Apple as long as your factory warranty hasn’t expired. Or, you can choose to take your chances with your iPhone 4 and hope it remains in good, working condition (I’d personally recommend the AppleCare option unless you’re planning on purchasing a different cell phone or the next-generation iPhone when it is released).