The way I see it, diigo only saves highlights for a constant URL. But many dynamic web applications add parameters to their URLs which are often only valuable for the server (sometimes as a replacement for cookies), but not for the client, because exactly the same content is returned.

To illustrate:
When we surf diigo's homepage, we discover the link
http://reviews.cnet.com/4520-9239_7-6654999-1.html
On this page we underline the paragraph about diigo.
However, when we search CNET for the "Top ten research tools", the link suddenly is slightly modified:
http://reviews.cnet.com/4520-9239_7-6654999-1.html?tag=feat.1
We will discover that all our highlights have vanished, although it's still the same contents.

How can this problem be countered?
I suggest that every user gets the option to maintain a list of such links. I believe that Regular Expressions would be suitable, but too complicated for most and probably to difficult to implement.
I think it would suffice, if one simple writes the beginning of the URL and then lists parameters for in-/exclusion.

The status quo is:
for all "" method=exclude params="". // include every parameter except for 'none'

For the example URL, it could be like this:
for all "http://reviews.cnet.com/" method=include params="". // only include 'none' <=> exclude all <=> ignore all parameters

For a Google search with the following URL:
http://www.google.com/search?hl=en&amp;q=diigo&amp;btnG=Search
for all "http://www.google.com/search" method=include params="q". // only include parameter "q"

What do you think about that?