How do you support this? Have you done a poll of mainstream scientists (or better yet - the 'best' ones)?

I have not done a poll of mainstream scientists. Aside from Shane Legg, the one mainstream scientist who I know of who has written on this subject is Scott Aaronson in his The Singularity Is Far article.

I was not claiming that I have strong grounds for confidence in my impressions of expert views. But it is the case if there's a significant probability that we'll see AGI over the next 15 years, mainstream scientists are apparently oblivious to this. They are not behaving as I would expect them to if they believed that AGI is 15 years off.

I haven't seen a poll exactly, but when IEEE ran a special on the Singularity, the opinions were divided almost 50/50. It's also important to note that the IEEE editor was against the Singularity-hypothesis - if I remember correctly, so there may be some bias there.

Can you give a reference?

I'd actually guess that at this point in time, a significant chunk of the intelligence of say Silicon Valley believes that the default Kurzweil/Moravec view is correct - AGI will arrive around when Moore's law makes it so.

This is interesting. I presume then that they believe that the software aspect of the problem is easy. Why do they believe this.

200 years? There is wisdom in some skepticism, but that seems excessive. If you hold such a view, you should analyze it with respect to its fundamental support based on a predictive technological roadmap - not a general poll of scientists.

I have sufficiently little subject matter knowledge so that it's reasonable for me to take the outside view here and listen to people who seem to know what they're talking about rather than attempting to do a detailed analysis myself.