It really depends on what you mean. With just the regular phone functionality, people are becoming less and less dependent with the web and email. The internet is changing the way people communicate, so phones aren't as important in communication. If you mean smartphones, then we're not dependent on them at all. If there were no more smartphones, people would just turn to computers. They are essentially the same thing.
Smartphones and Laptops are devices you can take somewhere and use it on the way. So, basically it has enabled people to Socialise with portable devices and tis means people may respond to an email or reply to something quick than usual. Search Advantages of Social Networking, Or Advantages of Social Networking on portable devices.