"I really worry about everything going to the cloud," he told the audience. He added that "it's going to be horrendous," with a lot of "horrible problems in the next five years."

Losing Control?

A key issue bothering Wozniak is that users could lose control of their cloud-stored material, such as turning over control of their rights in exchange for accessing the service.

Wozniak said that he wanted "to feel that I own things," while the "more we transfer everything onto the Web, onto the cloud, the less we're going to have control over it."

At various times, industry observers have also raised concerns about those agreements, which users rarely read. Potential issues include data mining of user material, or restrictions on how legally purchased material can be used.

Although Wozniak's criticism was largely based around the agreements that users accept to use cloud services, recent security breaches in cloud-based sharing and storage services have illustrated other weaknesses.

Earlier this week, for instance, Wired reporter Mat Honan reported that his iCloud account had been hacked on Friday, and that the intruder had remotely wiped the shared content on all of his devices -- including a MacBook Air, iPhone and iPad. The hacker also changed his Gmail account password and erased the contents on that account as well.

'Wasn't Password Related'

Honan said he has "confirmed with both the hacker and Apple" how the intrusion occurred. He noted that it "wasn't password related," and that he had created a 7-digit alphanumeric password which should have been reasonably secure . Instead, Honan said, Amazon provided four digits of a credit card number of his to the hacker, and Apple used that fragment to perform identity verification.

He added that Apple is making an attempt to help him recover the data erased on his MacBook.

Also recently, a list of an unspecified number of Dropbox names and e-mail addresses was stolen when a Dropbox account of an employee of that service was hacked. The account contained the confidential list of information. Apparently, the employee's account was hit after some passwords had been stolen, and the company noticed when users began complaining of spam that was being sent to their Dropbox-only e-mail addresses.

Dropbox has announced several new security measures. Within a few weeks, for instance, a two-factor authentication will be implemented. This will require two kinds of identity in order to sign in, such as the password and a temporary code sent to one's phone.

The company will also use a new automated mechanism to help identify suspicious activity, and a new page will allow users to see all active log-ins to an account.

Keith: