Populicio.us was a service that used data from social bookmarking site del.icio.us, to create a site with enhanced statistics and a better variety of 'popular' links. However the Populicio.us service has just been taken off air, because its developer can no longer get the required information from del.icio.us. The developer of Populicio.us wrote:

"Del.icio.us doesn't serve its homepage as it did and I'm not able to get all needed data to continue Populicio.us. Right now Del.icio.us doesn't show all the bookmarked links in the homepage so there is no way I can generate real statistics."

This plainly illustrates the danger for remix or mash-up service providers who rely on third party sites for their data. del.icio.us can not only giveth, it can taketh away. Now, it appears as if del.cio.us celebrated its second birthday by re-designing its homepage. I'm curious if they intended to take away the data that populicio.us needed to operate, or was it an unintended consequence?

As Andy Baio pointed out, "the Delicious New Popular is pretty good". Hmmm.

I'm sure it was unintended, but the fact is del.cio.us effectively hobbled populicio.us with its re-design. Who controls the data is something that is still being explored in the Web 2.0 world - and I bet we see some more high profile examples of this 'giveth, taketh away' in the near future.

UPDATE: Fair points by both Dare Obasanjo and Ian Davis, who say that HTML scraping doesn't have the same level of obligation as an API.

Dare wrote: "An API is a service contract which is unlikely to be broken without warning. A web page can change depending on the whims of the web master or graphic designer behind the site."

Ian wrote: "This shows the distinction between content designed for human consumption and that designed for machine consumption. The human format will change for all kinds of reasons often simply as the site matures and its users become familiar with its workings. Machine interfaces change on a completely different timescale and generally stable over the long term."

Both great points. Populicio.us still lost their service because their reliance on del.icio.us fell away, but the lesson here is that screen scraping HTML comes with those risks by nature. del.icio.us or any other data silo still controls their APIs, but one would think they're more stable. Thanks Dare and Ian.