Google’s capacity to store your files will not double, but triple the company said Monday, rising from 5GB to 15GB shared across Google+, Gmail, and Google Drive. Google made the announcement today on its blog, just before the Google I/O developers conference that begins on Wednesday.

There is no question this extra amount of storage is a game-changer, but why? What is Google’s play here? Google has a propensity to give you access to more free, because you’ll end up doing something that makes it more money.

The 15GB of storage will be shared seamlessly across Google+, Drive, and Gmail too. From today’s blog post:

So instead of having 10 GB for Gmail and another 5 GB for Drive and Google+ Photos, you’ll now get 15 GB of unified storage for free to use as you like between Drive, Gmail, and Google+ Photos.

Interestingly enough, Google is making changes to its Google Drive storage page as well. Those of you that are heavy gmail users this change means you’re no longer limited to a 25GB upgrade in Gmail. The overhaul of storage to “across the board” means the Gmail ceiling has been lifted.

I am going on the record that this is a direct shot fired across the bow of all of the free storage companies, specifically Dropbox. Let’s quickly rundown the free storage players:

1. Dropbox – 2GB
2. Apple iCould – 5GB
3. Amazon Cloud Storage – 5GB
4. SugarSync – 5GB
5. Microsoft SkyDrive – 7GB

Now of this list, I’d argue that majority of you are most familiar, both by name and usage, with Dropbox. Disclosure: I’m a $99 yearly 100GB Pro user of Dropbox, and use 5.3/100GB. Here is what this announcement means to me: I could save $99 a year by switching to Drive, and its 15GB free offering. And there is the shot to Dropbox’s bow. Not only would Google Drive steal free users, because free users like more free stuff; but now those paying Dropbox users that are somewhere between 2GB and 15GB could now save essentially save $100 a year.

What portion of Dropbox’s paying users do you think fall in the 2GB-15GB club? I have to believe it’s a decent slice of its reported 100 million+ users. I do know this, if I were Dropbox right now, I’d sure be sweating…

Here are three ideas to whet your palate from what Google storage expansion across Drive, Mail and Plus means as part of their larger strategy:

1. The big appeal for free storage at the consumer level is that these individual end users will employ Google services at work. Back door entry to the enterprise, where Google has significantly smaller market share than Microsoft on the software side, and smaller market share than Apple on the device side (with smartphones and tablets).
2. Google could eventually monetize the consumer directly.
3. Combining storage across these three apps is another way for Google to grow access points to reach consumers thru advertising. More opportunity to learn (market research), and in turn, better target ads (something Facebook is going after with Home, Graph Search). It’s the strategy Google perfected with web search.