Many web people have been critical of Google's new Toolbar, which allows its users to choose to have the pages they view parsed for things like ISBNs and have them auto-linked to Amazon, or have Vehicle Information Numbers auto-linked to a VIN registry.
It's not a service I'd use, but I believe that it's the kind of service that is vital to the Web's health. The ability of end-users to avail themselves of tools that decomopose and reassemble web-pages to their tastes is an issue like inlining, framing, and linking: it's a matter of letting users innovate at the edge.
I think I should be able to use a proxy that reformats my browsing sessions for viewing on a mobile phone; I think I should be able to use a proxy that finds every ISBN and links it to a comparison-shopping-engine's best price for that book across ten vendors. I think I should be able to use a proxy that auto-links every proper noun to the corresponding Wikipedia entry.
And so on — it's my screen, and I should be able to control it; companies like Google and individuals should be able to provide tools and services to let me control it.
(Of course, this isn't to justify fraud or passing off, as when linking, inlining, copying, proxying or other munging of pages are used to deceive end-users or remove their freedom of choice. But fraud isn't bad because it uses proxying, or deep-linking, or inlining: fraud is bad because it's fraud, no matter what tools it employs.)
Yoz "Perl is Internet Yiddish" Grahame has posted a good, apoplectic, funny, point-by-point refutation of the major objections to the Toolbar. It's a clear-eyed explanation of why, even if you don't use the Toolbar yourself, you should support it and tools like it.
"The issue for authors and publishers is whether readers know they're reading text that's been modified."
And it's so ambiguous! Admittedly, in order for the web page to be altered by the Google toolbar, an "AutoLink" button needs to be pressed every time (it doesn't do it automatically), and the first time you press it this pop-up window appears which explains everything. Personally, I don't think that's nearly enough! A large claxon should sound, the screen should flash, and the user should get a phone call from a Google employee explaining the incredibly ambiguous and possibly-accidental button press. After all, the user might not realise that they had altered the content of the page if they were incredibly forgetful or stupid.
