With Facebook now public and sitting on a huge pile of cash, let’s turn the conversation to the social network’s most pressing competitor, Google. Google and Google+ don’t appear to present much of a threat to Facebook, but the game board was reset on Friday and tactics at both companies will change accordingly. Now Facebook has to find a way to grow revenue and users and will increasingly bump up against Google’s huge advantages in search and apps. For Facebook to achieve its goals, the company will have to enter both spaces with gusto.

Google has learned how to leverage its strengths and suddenly one of those strengths is Facebook’s success. Now that Facebook is a $100 billion company, it doesn’t hurt Google to be number two in that space. Who else is? Pinterest? Instagram? Twitter? None of those services offer a full-fledged social network for those who do want a Facebook alternative, and some people will.

There’s nothing that unique at Google+ to cause people to leave Facebook for it. But there are compelling reasons why publishers might decide they need to make use of it, chiefly for search rankings. If the publishers think they’ll get better rankings, they’ll help push it along, which means Google+ will continue to grow whether people actually use it or not.

In January, for example, Google added a new box promoting people who are on Google+. If you’re not on Google+, you can’t appear in the box. Do a search for “music,” and someone like Britney Spears was showing up. The following week, Lady Gaga – who ignored Google+ up until that point and so didn’t appear in the box – joined. Search for music today, there’s Lady Gaga.

That’s a game changer. Google has used the attraction of its search page to convince publishers to effectively jump start its social network. It probably won’t overtake Facebook. It might always remain a distant second to Facebook. But it has given Google a much more viable competitor than ever before. And if you’re a publisher, you want to be part of it, because it has a huge impact on your visibility in Google search.

The guy who really gets this is Danny Sullivan over at Search Engine Land.

Google has other apps it can leverage like GMail, for example, and Google Docs. And of course there’s basic search, itself. Looking at GMail as an example, it has been in Facebook’s interest to keep users communicating inside the social network rather than extending relationships outward through a mail client where they’d risk escaping from Facebook entirely, talking among themselves. In its new role as a grownup, however, Facebook will ultimately have to face the external mail needs of its members it if intends to continue subscriber growth, so I’d look for some sort of FMail service with clever social media hooks.

Of course the most obvious way for Facebook to take it to Google would be in basic search, but that’s where I’d see Facebook playing a similar card to Google and accepting number two status in search by acquiring Bing from Microsoft. This makes sense for both companies since it would probably happen as a stock deal with Microsoft increasing its Facebook holdings (and influence). For Facebook buying Bing this week would cost a lot less than it would have last week, since it can pay with bloated stock.

There’s no do-or-die in this, but Facebook and Google are lining-up as each other’s main enemies and in order to compete each will start to look a lot more like the other.