Dublin boy Jonathan Swift wrote the following little ditty:
"So, the naturalists observe, the flea,
Hath smaller fleas that on him prey;
And these have smaller still to bite 'em;
And so proceed, ad infinitum"
Sounds like e-commerce proxy chaining to me
"So, an IDP issues assertions in XML,
On which an SP might choose to sell;
And these have other SPs willing to trust 'em;
And so proceed, ads infinitum"