I think that cell phones and internet have forever changed the social dynamics of our time. Much like the invention of the telephone and television - communication and entertainment forever changed. Some argue that these inventions are destructive to social interactions, with studies indicating that people have become more withdrawn with improvements in technology (even though their "friend lists" have probably quadrupled in size). However, cell phones and internet have likely increased business capability exponentially - with more opportunities than ever to create powerful communication tools while at the same time lowering the barrier to entry for many small businesses. As some of the other commenters have mentioned, they have been essential in many recent political issues - opening up the flow of information and potentially increasing the possibilities for democracy, particularly in the Middle East and Northern Africa.
All that being said, they've also made people get into more car accidents, find it harder to make small talk in line than update their Facebook - and have made ruder people ruder and more annoying with their cell phone habits. I guess you take the good with the bad though. When TV was invented and made widely available for most to afford, people thought it was the end of the world - that peoples brains would rot. However, it's proven to be one of the most effective communications mediums of our time and something that most people would not do without. I guess time will tell, but the same may eventually be said about internet and cell phones.