You mean his suggestion to use <input type="submit" name="delete-id-1" value="Delete this address"> ? There a couple problems with this: (a) no nested forms, so it can be difficult to put a submit button in an arbitrary location, and (b) there remain links that are not "safe", but are truly link-ish, and (c) there's less control available over buttons, which can be a problem in some circumstances (buttons tend to be visually weighty, and CSS controls are limited).
Unsafe GET links did not start with Web 2.0 apps; they are as old as the web itself, and old and largely unmaintained web applications have these bugs. The idea that we should "fix" these applications because GWA exposed a "bug" is incredibly unrealistic. Though in a practical sense, it does seem that this incarnation of the GWA is somewhat improved, as it doesn't prefetch links with variables (i.e., ?). Maybe that will be enough, I'm not sure.
Web Forms 2 supports nested forms in XHTML. It also supports a form attribute on form controls so you can associate them with any form even when they are not a descendant of any. Quite cool and there are some experimental implementations out there.