The beauty of the cloud is that you are able to access your files anywhere there is an internet connection. If you are halfway around the world and need to know where that Tuesday meeting after you get back is and with who, you can go to an online product like Google Calendar to find out. Items in the cloud do not take up space on your hard drive.
Needless to say it isn't perfect and there are issues and concerns the biggest being privacy and security. Since you are trusting your data to a third party you want your information to be secure and not easily accessible to those you wish to keep it away from. You also want to be assured that the provider will not lose your data. As we know Facebook has had security and privacy issues. I believe that as we move more into the cloud, these issues will resolve themselves. Security and privacy will be much improved because of competition and technological advances. Another issue is the accessibility of the data. What if the internet goes down or either you or your provider lose internet access? The quick and short answer to this is unless you have backed up your data locally you have to wait until access is restored. That said, web services are continually improving as to access and security. Like any service providers there are good and bad. Keep in mind if your hard drive crashes or you cannot get on your computer for some other reason, having backups is important. Cloud applications do guarantee the safety of your data. Any reputable company storing your data online will have backups of their own. I will say this in closing for those of you who do online banking and/or get credit card statements online. The bank statements you see in your account where you do your online banking that saves you space(you do not need a hard copy of them) is in the cloud as are the credit card statements you see in your online account. Businesses are starting to move their data into the cloud accessing and storing it there.