On the topic of "Viral Videos"

One of the major things to come with the proliferation of Internet technology is the ability to access and upload web video.

This was the topic of conversation for our lecture this past week.

One of the most interesting things that we came upon were some of the figures about web video such as:
-total videos uploaded to youtube – 78.3 million
-average video length- 2 minutes 46 seconds
-time it would take to view all of this 412.3 years
-average age of uploader: 26.57

Of course those numbers are constantly changing, however the point I'd like to examine is what really makes a viral video viral.

At our discussion we discussed that for the most part there are 4 types of web video:

-business generated

-business generated but customized

-business initiated, user-generated

-user-initiated and user-generated

These categories tend to be the general kind of videos that we as users experience. However, my thoughts are what makes a viral video, and do any of these in particular make better viral videos?

In general, one would assume that business backed videos with seo campaigns and marketing campaigns can push any video to be a "viral" while the more user-created may have a harder time or requires a bit more luck to really reach the same level.

We learned that it really doesn't take that many people to begin the cycle of sharing and take a video viral, but in general does a marketing campaign, seo campaigns take away from the quality and notion of a viral video? Do we really worry if a viral video needs to be user-created and initiated?

Thoughts?