What is Interactivity?

My definition of interactivity is something, generally electronic, that a person can use and learn from or communicate through by...well, interactivity. Like a website or computer program. You click on certain buttons/icons and information pops up etc. from witch you can learn and gain something from, such as information or even downloading movies and music.
Kiousis, on the other hand, has a different definition of interactivity, two of them in fact. He saw interactivity broken down into communication and non-communication. Under communication Kiousis discussed that "any discussion of interactivity inevitably draws from its roots in Cybernetic theory." And he defined communication as what "is seen as a dynamic, interdependent process between senders and receivers." Kiousis explains non-communication as the "broader term of ‘interpersonal communication’ – which can occur in both technologically-mediated and unmediated contexts – rather than employing face-to-face communication to avoid such concerns." That's nice, but a little too complex for my liking.
The Long Tail theory is definitely interesting, and after reading the article on it I can see how it could possibly be used for future business, but at the same time I can also see how it could mess things up. Thanks to Amazon people and find almost anything they want, new or old, and are able to wright reviews and suggestions for others to follow. But who is to say that what people say is good really is? I mean if I got a group of my friends convinced that the new Britney Spears CD was awesome (and that would probably take some doing as I don't even listen to her) and got them all to post great things about it, and consequently a 100 people bought her CD because 20 of my friends wrote that if you liked so and so you'd really like Britney Spears, is that really a good thing if it turns out the CD is crap? Granted, that a fabricated scenario, but a good example of how the Long Tail theory could go bust. Then you'd have 100 pissed off customers who would then probably write all kinds of bad things about the CD AND Amazon.com. But that's just the negative side to the story. The positive side is yea, that looks like it could be used by companies to promote old CDs etc and generate more revenue. People listen to what others like themselves write on these types of sites, even if it's not always true, or at least not true for your tastes.