Its always a trade off whether to own or take it on rent. Like some time its very difficult to buy a luxury house but you can take it for rent. Actually its not applicable to only house we can extend it to car, furniture even girl friend also :p The advantage of taking on rent is as we don't own it we only pay as we use. The trend is slowly moving towards pay for usage of software also. For example to write this blog i don't have to own a blogging site, I can use google service with all other users. Certainly I can customize it . I agree i cant customize it to the extend if i own it. But it is really economical. Well the idea can be roll into all possible s/w. Lets think a scenario when the SAP will host all its enterprise solution in its server and all the company will use through web. Well it has challenge like security, customization according to user ... But i feel the industry is mature enough and ready to take this challenges. Infact TCS is already started with iON for small scale and mid scale industry.It reduces the software cost dramatically and can be accessible to lots. People say it software as service, software on cloud....Its just renting software... So before all the big player enter to the game lets rent some thing :P
