Google+ has seen some good initial uptake from early-adopters in its first few weeks. But how will it leverage developers and partners?

In order to really build value around Google+, of course Google will integrate it with their other products, including Search, Gmail, and more. That will get it in front of a lot of people, many times a day.

But that’s not enough. Google+ has to grow as a product – it has to innovate and evolve, to stay ahead of everyone else. And it has to get hooked into other products so that it become part of everyone’s workflow even when they are not in a Google-owned site or app.

Even with all the engineers at Google, Google+ cannot innovate or integrate fast enough on its own: it has to find ways to get third-party developers to do some of this work in parallel.

The way Twitter evolved was through their API: They leveraged a huge army of free engineering talent around the Web to build them into everything, and to prototype features for them to cherry-pick into their core app.

What about Google+? Will they innovate via an API in the same way? Actually I think it may happen a bit differently.

Google+ has something unique to leverage: Chrome, a platform Google owns. While Google+ may release an API as well, I think Chrome will be more of an early focus and leverage point.

First of all, Chrome is easy to extend and it has a marketplace built in now. Secondly, by driving developers to extend Google+ on Chrome, Google kills two birds with one stone: they get innovation on Google+ and they make Chrome even more necessary and valuable – it will be the best way to use Google+.

I think Google+ is about to explode in new features, and most of them are not going to come from inside Google: They’re going to come from outside developers extending Google+ on Chrome. And this may be Google’s trump card.

Within 6 months there could easily be at least hundreds of new Chrome extensions that add functionality to Google+ and within 12 months there may be thousands of them. If this happens it could completely change the game for Google, Twitter, and their developer communities.

Most of these Google+ Chrome extensions will be features, not full applications. The Google+ product team and M&A team will be able to sit and watch to see which ones get the most usage, and the best of those will become “build vs. buy” candidates for addition to the core codebase of G+.  Think of it as a massive distributed A/B test, a decentralized genetic algorithm to evolve the best new features for Google+.

As these Chrome extensions come out from all directions, they will increase adoption and usage of Chrome, and since they won’t be available on other browsers, Chrome will gain market share. So not only will Google+ increase traction, so will Chrome, and ultimately the entire Google platform.

Many of these Chrome extensions will be free, but some will be paid apps. And Google will share in those revenues. This could be a huge driver of Chrome as a platform in its own right and could really make the Chrome Web store into a big business.

But what about a possible Google+ API; where does that fit into this equation? I think it will certainly happen, but I bet Google will focus more on Chrome extensions first because an ecosystem of Chrome extensions driving eyeballs to Chrome and Google+ simply has greater value to Google than third-party apps using an API.

A Google+ API would be great for developers and third-party businesses, and ultimately for streaming Google ads into G+ streams in third-party apps. But it will not drive adoption of Chrome. Therefore, I’m willing to bet that Google is going to delay the Google+ API for a while. That will leave developers no choice but to make Chrome extensions as a way to build on the Google+ platform. And they will. Every developer I know is drooling about this right now.

But one thing that’s important to note – Google has some work to do to really enable a massive upsurge of Chrome extensions for Google+.

Some of the developers I work with have been poring through the G+ JavaScript and data streams. And what they’ve found is that Google has not made it easy to augment their streams. The code is highly obfuscated and it’s really hard to find what you need in there.

Writing third-party Chrome extensions to augment G+ is doable, but not nearly as easy as it should be. One developer called it “a real pain to find what you need in their code.” Google should make this much easier by making their G+ code and data much more accessible, readable and extensible by third-party developers on Chrome.

If Google+ can add more transparency and developer hooks, it could be a big win for them. Google’s famous “Not invented here” syndrome may then take on a new meaning – much of Google+ may literally not be invented inside of Google, and will happen in parallel all around the Web, leading to massive parallel innovation and developer adoption.

Now what should Twitter do about this? How should Twitter respond, and what should their strategy be? I think Twitter has to change their strategy and focus on their API: Here are my specific recommendations.