The new Facebook Home may be built on top of Android, but investors apparently don’t see that as a positive for Google. At the close of the market on Thursday, Facebook’s stock was up 3.09% to $27.06 while Google shares fell 1.38% to $795.07.

In terms of market capitalization, Facebook added roughly $2 billion to its previous market cap of $62.48 billion to close at $64.4 billion, while Google shed about $3.67 billion off yesterday’s market cap of $265.8 billion.

By comparison, the NYSE Arca Tech 100 Index, which doesn’t include Facebook or Google but does have Apple and Microsoft, was up 0.62% for the day.

Facebook on Thursday debuted Home, a new app launcher and home screen for Android. It also announced a new program for partnering with handset vendors and carriers on the software and unveiled the first phone to come with Home pre-loaded: the HTC First on AT&T.

Home is bound to be a win for the Android platform, but, oddly, it might not actually be a win for Google. This is an instance where Android’s openness can actually work against Google’s own interests, since Facebook has the power to gradually oust Google’s own services on the phone and promote its own. Considering that Facebook CEO Mark Zuckerberg said he was “sure” that Facebook Home’s cover feed will eventually get ads, Google’s own advertising income is at risk.

In effect, Facebook is wielding Android in its competitive fight against Google. Suffice to say, this is going to be interesting to watch.

The Next Web’s Alex Wilhelm went hands-on with Home and found Android’s stock start screen to be “quite hidden”. Facebook is clearly trying to keep users within its ecosystem here, and that’s going to be to the detriment of Google.