I've found a great article in Wired, written by security guru Bruce Schneier, Everyone wants to 'own' your PC. The reading is fascinating, as it goes through how various software companies try to control your computing experience.

When technology serves its owners, it is liberating. When it is designed to serve others, over the owner's objection, it is oppressive. There's a battle raging on your computer right now -- one that pits you against worms and viruses, Trojans, spyware, automatic update features and digital rights management technologies. It's the battle to determine who owns your computer.

Schneier explains why Microsoft, Symantec, Sony and Google (and many others, namely spyware/adware companies) want to influence the way people use their computer. He explains how Secure Computing and DRM are going to make things worse. His conclusion is simple (emphasis mine):

If left to grow, these external control systems will fundamentally change your relationship with your computer. They will make your computer much less useful by letting corporations limit what you can do with it. They will make your computer much less reliable because you will no longer have control of what is running on your machine, what it does, and how the various software components interact. At the extreme, they will transform your computer into a glorified boob tube.

You can fight back against this trend by only using software that respects your boundaries. Boycott companies that don't honestly serve their customers, that don't disclose their alliances, that treat users like marketing assets. Use open-source software - software created and owned by users, with no hidden agendas, no secret alliances and no back-room marketing deals.

Just because computers were a liberating force in the past doesn't mean they will be in the future. There is enormous political and economic power behind the idea that you shouldn't truly own your computer or your software, despite having paid for it.