This is why everyone who uses Bitcoin should immediately set up an offline private key for just such an event.
I use Keepass in conjunction with my wallet's password (a cipher generated by Keepass, brute force password cracker will never break it), I know the master password of my encrypted password database that has all of my other passwords for encrypted things. Both my wallet.dats and Keepass databases are auto-uploaded to my FTP every night. My wallet's themselves live on a RAID-5 array. I'll be setting up a DropBox as well for a tertiary backup. A 4th backup will be coming soon in form of a USB backup drive for my file server.
With crypto currencies you can never have enough backups and methods to ensure your money stays where you can access it. Key phrase: your money
It is more true than any other banking system ever now. Your funds are entirely in your care and trust until you specifically tell it to do otherwise (a transaction is a transfer of ownership in Bitcoin).
Encrypt and backup you're wallets to multiple locations with automation, create backdoors with private key paper wallets for your main savings address(s), maintain you're computer, anti-malware systems, and firewalls.
Once Bitcoin was a novelty, and now it is quickly becoming a hot topic and a power player in the shape of things to come. Imagine your grief when that lost .dat file, a measly amount of information, is worth 1000x what it is right now, or in a more distant future a lot of Bitcoins still worth a lot in the neo-economy. Makes a backup drive and a few cloud accounts look pretty attractive in comparison to screwing yourself out of several thousands or millions because "you''ll do it tomorrow"