Yahoo announced last week at the Web 2.0 conference that they are opening up their entire network to developers to build apps and mashups. The announcement was covered by Greg Sterling for SearchEngineLand and the brief 14 minute announcement and explanation by Yahoo CTO Ari Baolgh has been covered by very well by Michael Arrington at TechCrunch. There’s also a wonderfully prescient view from Loren Baker at SearchEngineJournal – from a YEAR ago, which he looks at again in the light of Yahoo announcements this past week.

Here’s a video of the Ari Baolgh Web 2.0 Keynote presentation, thanks to Yahoo Video:

I got to attend a later, Friday Web 2.0 presentation titled “Yahoo! and Open Platforms, A Deeper Dive by Yahoo Chief Architect of Platforms, Neal Sample, who delivered as promised with a presentation on how the whole Yahoo Network, including Yahoo Mail, Flickr, Answers, etc. all get reworked and rejiggered to make this one massive Social experiment.

I’ve taken a look elsewhere at the Y!OS or Yahoo Open Strategy idea through the lens of privacy concerns this may raise for the 500 Million claimed Yahoo users.

But privacy issues aside here, this announcement could truly gain Yahoo an increased bid from Microsoft now that the MSFT deadline for a response from Yahoo has come and gone this past weekend. Watching the video above, one has to imagine Balogh seeing this as a presentation directly to Microsoft and picturing the camera as Steve Ballmer – the video being made available first to Michael Arrington at TechCrunch (hmmm what Yahoo strategy!), who put it well in his coverage, saying:

They still, of course, have to actually launch this massive project – for now it’s all ideas and vaporware. And no one knows what Microsoft thinks of all this, or what happens to YOS if that deal is done.

Now let’s see how the press reacts Monday morning and what noises Microsoft makes in light of these Yahoo announcements. Microsoft invested $240 Million in Facebook not long after they announced a much smaller scale “Open” strategy, that’s the same Facebook which is not even participating in the Google Open Social model – but Yahoo is participating and – one might argue – leading in this monstrous experiment that must have Microsoft groaning in agony.

Microsoft, open? They gotta hate this Yahoo Open Strategy (YOS) idea. Google moves to undermine Microsoft on Google Docs, Yahoo moves to undermine Microsoft takeover bid by open-sourcing their entire network (hmmm what Yahoo strategy!).

Despite my privacy concerns, I’m excited at what this may mean for search in general – not just for Yahoo – but for the web and how search works. I’ve been critical of Yahoo for their massive acquisitiveness in the past and have never understood how they failed to take advantage of their massive audience to become a social networking leader (Geocities anyone?).

This is big and I can’t imagine how this could fail to evolve search and social media. It will affect everyone if they pull it off successfully and if Microsoft doesn’t screw it all up for them with a proxy battle and eventual win.

I never could have imagined myself in a position to cheer for Yahoo, but I may … I just may. 😉