I totally agree there is something wrong here.
If I insert something like this in the html editor
<img src="/wp-content/uploads/2011/08/somefile.png" alt="Alt text"/>
then browsers that support SVG will display the SVG file, and those that don't will display the png version. Granted this won't work on some very old browsers but I bet more browsers support this than support flash, especially given the proliferation of mobile browsers over the last few years.
That, incidentally, is more or less the way the Wikimedia websites do it.
But here goes, I switch to the wysiwyg tab then back to the html and, oh look, WordPress has re-written my html to download a macromedia object. That's just plain wrong on two levels:
1) I don't want to use flash, for the reasons previously explained ie it is NOT universal and it is NOT required for this purpose
2) I thought the whole point of the html editor was that it was for me to write the code, but apparently now WordPress can we-write my html for me, to do something completely different
3) I go edit post, switch to wysiwyg, switch to html, haven't made any edits whatsoever, and yet wordpress has modified the content!
Did I say 2 levels? Well I stopped counting at 3. Regardless of flash plugins, surely any html I enter manually should be left alone by the wysiwyg editor, unless I edit that particular section explicitly.