Dropbox accidentally turned off the password feature on their file sharing service last Sunday from 4:54pm until 8:41pm. The file sharing service was eventually restored and secured at 8:46pm. Between those times, anyone can access any of the 25 million Dropbox accounts by simply typing in a random string of characters in the password field. Dropbox said, less than 1 percent of the accounts were accessed at that time period and will continue to investigate if any accounts were compromised.
It just shows you that online services such as Dropbox, and social sites such as Facebook and Twitter are not 100% secure. If you’re concerned about the security, then you shouldn’t really place any highly sensitive information on any of the online services. If you must, then you should use the highest encryption standard you can find. I recommend that you use AES-256 encryption. If you’re a Windows user, you can use the popular compression program called 7Zip. For Linux or Ubuntu users, you will find more information here in this forum.