> Well, the problem is that for complex types you can't easily convert from one to the other, because only the program doing the copying has all the info.
Actually the idea was that the application doing the copying provided the data in its native/internal format, which by definition should have all the information. It could always define an x- or a vnd. mime format for this and provide whatever converters it wanted to transform that data into other formats (they could probably double up as export filters too).
> Example: If you copy a bit of a webpage, it can be either plain text, the raw HTML code, or formatted text depending on the style etc. Converting to plain text is almost always possible, but anything else doesn't really work. So a single mime type isn't always sufficient.
In this case the native format is presumably "text/html", which should be convertable to either plain text or formatted text without the copying application even having to provide its own converters.