online office application

More and more businesses are using Online Office Applications.  What are the advantages and disadvantages of using using these types of applications?  Why would a company want to start using this type of solution?  Be thorough with you answer. 

I am refering to Spreadsheets, Word Processing and Presentation Software.  Please do not start a thread about job applications or other types of applications that can be submitted online.  The application for this forum is referring to the office software only. 

I only need a short answer for today