I have a score of different motives myself. Self-expression, exploration of a medium, communication with others, sharing ideas.

Hopefully, all this media-making will lead to something bigger.
That little chunks of mine or your media can be used for something else. Recontextualized. Used to show what - for instance - Amsterdam was like in 2006. Or whatever.

We are all ambassadors for our time. We must make the most of that fact.

Personally I think my ego is malfunctioning, I have real trouble putting photos or video of myself on the net, or even having my own blog, but I can quite happily post long messages to forums/groups and comments on blogs.