Mobile me is a great service, if you use it to it's entirety. It cost $100/year.

Having all your info synced in the cloud is great though, for you do not need to plug your iPhone into iTunes every time you add a contact or create a event. If you like the idea of having your information synced with across all devices and computers, and being able to build websites with ease, then spring for cash, otherwise it might not be worth it.

Info on mobile me:

Push email.

When you join MobileMe, you get a me.com email account that’s always up to date. New messages are pushed to your iPhone or iPod touch automatically, and you’re notified the instant they arrive. MobileMe constantly checks for new messages, so you don’t have to. And when you use MobileMe, you’ll notice that the inbox on your iPhone looks a lot like the inbox on your Mac at home, which also looks a lot like the inbox on your PC at work. That’s because it is. Read messages are marked as read, and all your folders are exactly the way you left them, no matter what device you use to check your email. Last but not least, your MobileMe inbox is entirely ad free and includes spam and virus protection.

Push contacts.

With MobileMe Contacts, your entire address book is accessible from your computer, your iPhone, and on the web. Say you meet someone and add that person to Contacts on your iPhone. MobileMe automatically pushes the new contact to the cloud, and in seconds it appears in Address Book on your Mac or in Outlook on your PC. You don’t have to connect your iPhone to your computer or do anything at all. Your new friend's information — his phone number, email address, photos and notes, such as “sat next to me at the parenting seminar” — is exactly where it should be, anytime you need it.

Push calendar.

MobileMe keeps your calendar in sync across your Mac, PC, iPhone, and iPod touch, so you always know where you need to be and when you need to be there. Change the time for your doctor’s appointment on your computer at work, and it’s automatically updated on your iPhone — no docking required. Add an event on your iPhone and it appears in the Calendar application on me.com in seconds, then syncs to your computers. You can even manage multiple calendars. So you’ll never miss a lunch date, soccer game, or important meeting again.

Works with the desktop applications you know well.

MobileMe keeps your data in sync across the applications you use every day — Mail, Address Book, and iCal on a Mac; Microsoft Outlook on a PC (Windows XP or Windows Vista); and the built-in applications on your iPhone or iPod touch. All your information stays up to date and is right where you want it, so there’s no need to learn new software or change your day-to-day routine.

Find My iPhone and Remote Wipe

It’s human to misplace things, even your iPhone. The good news is that if you do lose your iPhone, MobileMe can help you find it. Simply enable the Find My iPhone feature in MobileMe settings on your iPhone.* Then anytime it goes missing, log in to me.com from any computer and use Find My iPhone to show its approximate location on a map. Play a sound to help you find it yourself or display a message on the iPhone screen to help someone else return it to you. And if you haven’t set a passcode lock, you can remotely add a four-digit passcode to keep your iPhone secure until you have it back.

Remote Wipe.

If you’re concerned that your iPhone won’t make its way back to you, you can initiate a remote wipe at me.com.* This restores your iPhone to its factory settings, ensuring that your personal information is nobody’s business but your own. If you eventually find your iPhone, you can restore your latest email messages, contacts, and calendars easily. Simply connect your iPhone to your computer and use iTunes to restore the data from your most recent backup. Then just enable your MobileMe account on your phone.

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