This is the best approach I've found for making it easy to copy MathML from a web page. Together with Native MathML it allows me to copy MathML and paste into an HTML editor.

What would be a killer feature for me is if it allowed you to copy a chunk of text which included multiple mathml formula's and pasted the text and the embedded formulas. Currently, it doesn't seem to copy anything unless you select a single mathml formula.