Everything old is new again?

I read C4L's blog, and one of the things he's good at is skewering hype. In the process, he's pointed out some interesting similarities between new and old technology:

1. REST and POX
2. AJAX and DHTML
3. SOA and Web Services
4. PubSub and Push Content
5. Tagging and META-tags
   

In each case, something has definitely changed, to make cool that which was uncool and new that which was old. What is it?

1. REST is arguably a well-thought-out subset of POX that doesn't suck. POX + design patterns + exploiting HTTP's natual shape. What changed? Google showed us what was possible, and proved it could be done in the wild, outside of intranets.
   
   
2. AJAX is arguably a set of design patterns that use DHTML but don't suck. It came about after new school web design gained mindshare. Only after the browser technology in Gecko and Opera caught up with the standards and showed us what was possible, and only after people started validating, stressing on semantic XHTML, and using CSS to the full, did people truly begin to accept and explore the power of JavaScript.
   
   
3. Web Services is a small collection of good standards (SOAP 1.1, WSDL, UDDI) floating in a sea of untried, unimplemented, vendor-specifc and overly verbose (even for XML) 'standards' (SOAP 1.2, WS-[*]).
   
   SOA is WSs minus the suck: it's a philosophy that brings order to the chaos, built around the idea of presenting a unified model of your data upon which processes can be built & designed.
   
   WSs don't suck, but has suck potential, and SOA recognises that there's more to the special sauce than protocols or standards, and adding new ones doesn't help.
   
   
4. Push was crap. An unmitigated disaster, foisted upon unsuspecting analysts by dotcom droolers and entertainment hype-droids trying to turn the 'Net into a big, dumb television.
   
   PubSub, in contrast, multicasts and pointcasts data that people actually want in realtime, such as RSS feeds, as opposed to that which would rightly expressed in a collection of banner ads, where geeks can safely ignore them.
   
   
5. The difference between tagging and meta tags is transparency and control. Meta-tags are not transparent to the end user, but hidden away in the source. Meta tags are HTML-centric and intrinsically per-page, whereas normal tags can be per object, no matter the layout.
   
   The control issues where Technorati may have slipped upa little. Tags are nice bceause they're per-site, and each site has absolute control over their architecture. This is why I believe Flickr and del.icio.us work so well. With Technorati, they surrender this control to external users. We'll see how this works out.
   

I don't know why, but I have far more vitriol for old-skool Push than for any of the other dead ideas.