I have recently become a convert to the idea of putting as many as possible of my talks, posters and lectures on the web (see current progress here).
On March 25th I gave a talk on Cinfony to about 30 people at the ACS National Meeting. As soon as I got back, I put the talk up on Slideshare and inserted it in my blog. There have been 451 views in the month and a half since.
Because of this, now I'm going back and digging up all of my talks and posters and putting them up both on Slideshare and on my website. Naturally, I'm going to include the original file (typically a Powerpoint file) as one day Slideshare will be no more.
The funny thing is that although few scientists tend to provide their talks (notable exceptions are Rajarshi and Jean-Claude Bradley), I find it hard to think of any disadvantage. The whole point of giving talks and presentations is to publicise your work and surely your website is equally important in this regard. Indeed, many people might prefer to click through a presentation that explains your paper in bullet points rather than wade through your scintillating prose.
Another good question to ask is whether there's any difference between the audience that might have seen the talk at the conference and those that would have seen it online? The conference audience (especially at the ACS) would be more of the PI variety than the postgrad/postdoc. And I would guess that it would be the other way around online.
If you have any thoughts on whether this is a good/bad idea or know anyone else that provides all their talks, please leave a comment below...