XHTML copy and pasting *with* format (and potentially, meaning)

Please see http://www.netsnippets.com .
If you are not under windows, then please at least look at the concept,
perhaps the screenshots.
Netsnippets, regardless of detail implementations, is perhaps the best
standalone program of its kind. A browser plugin, could also be a way to
implement something like this.
The goal? I see something on a page, I select it, I copy it. *With* format
and all.
One simply draws a rectangle, for instance, and voila, all text, pirctures
whatever, gets copied and stored for future reuse.
The problem? it does not save formatting.
Question: Why?
Question: Could it be done?
Question: What would that require, both from XHTML and from CSS?

I believe there might be some DOM aspects and some CSS aspects to consider.

Regarding the DOM...well, it seems to work. Question: is there any problem,
any example, any use case in wich this sort of mechanism can fail? Could
some variation of the functionality be achieved at least, if so? Would any
change to XHTML help, or be needed?
(Side-note: if separation of structure from semantics gets
implemented...then perhaps the DOM group should consider something like
GetElementByMeaning? If so, we need to decide and tell them, to give them
some time)

Regarding CSS, and at least asuming the page author *has* used it whenever
possible...can just the relevant rules be extracted? Not just the whole
document CSS, be it just one sheet or many, but just the minimum required
for identical reproduction of the selected area?
I hope we all understand that this discussion should probably not be carried
here.
I figure it most likely pertains to both the DOM and CSS lists.
We can, in fact, do just that. Please feel free to post it wherever it
corresponds even if I did not yet. And let's keep it brief here, please.
My sole reason to mention it here is the bit that says "What would require
from XHTML (if any)?".
Or perhaps even "Is there something XHTML could do to facilitate such
functionality, given I do not see it implemented anywhere?".
I mentioned the other areas here simply cause it was needed to describe the
general idea.
 Fernando Franco