jQuery's Data functions

jQuery's Data functions


I was recently having a discussion with a fellow developer who was
writing code that set custom html attributes to various nodes to save
information that'd be required later when working with them.
I asked him why he wasn't using jquery's built-in support, Data for
storing that information in the nodes. He responded saying, he
woulnd't be able to use jquery's selectors to query against the dom.
$("div[custId=5]") //etc.
That made me wonder, why isn't there some sort of support for querying
the values in the jquery.data from within a selector. I'm aware I
could write a whole .filter(...) function but thats extrodinarily
wordy and defeat the purpose.
I was wondering what others thought of this, and how useful the data
functionality is to them in this regard.