When you look at certain questions with hundreds of answers like this one for instance, the answers are displayed in pages. To rewrite this into an AJAX setup would probably take a significant effort.
My hunch is that this sort of thing will come some day -- when more and more questions have pages upon pages of answers -- but probably not for at least another two years...
Now for specific questions or responses like these two:
Why does dust stick to rotating fan propeller?
Where are the necessary places to be appended with % to remove unwanted spaces?
You could consider suggesting edits to the lengthier responses by, for example, trimming those pictures down and placing them side by side.
Just my $0.02.
The accepted answer should be in the first row ...
this isn't specific to your feature request. But it's something that the more experienced users may quickly vote you down for because we already have several methods of sorting answers. – M. Tibbits Jul 10 '11 at 3:15