Here’s a riddle: what do you do with 100 million active users and $400-million of freshly-raised venture capital?

Answer: Pretty much anything you want, which can be a good or bad thing depending on your perspective.

That’s the situation facing Twitter, which has a “truck load” of money to do whatever it wants. With no need to do an IPO or be acquired, the world is Twitter’s oyster. It can make acquisitions, drive hard into different businesses such as advertising, analytics and data aggregation/distribution, or as GigaOm’s Mathew Ingram suggests, it could become a publisher. Flipboard, anyone?

Heck, Twitter could pull a Hewlett-Packard and completely reinvent itself by making a major acquisition. This is admittedly a far-fetched idea but given how crazy the high-world has been turning these days, you never know! I mean Michael Arrington is no longer working for TechCrunch, and Carol Bartz claims Yahoo “f@$ked me over”.

Data = Advertising Revenue?

So how does Twitter and CEO Dick Costolo move forward? The nice thing about having $400-million is it provides lots of financial latitude. The problem with having so much money is there’s a lot pressure to do something dramatic. Maybe even do something like create a business model!

The lowest hanging fruit for Twitter is clearly advertising given Twitter could crunch the vast amount of data it generates to deliver extremely targeted advertising. While Twitter has been slow off the mark to embrace advertising, my take is users will quickly accept it as part of the landscape even if Twitter decides to aggressively drive forward. There’s no reason why Twitter’s Promoted Tweets shouldn’t be as effective and lucrative as Google AdWords.

The thing is it is difficult to see how Twitter could spend $400-million to blow out its advertising business. So how does it spend all this money?

Acquisitions, Anyone?

Well, there are a bunch of acquisitions (e.g. TwitPic, UberMedia) could make but they could eat up $50-million to $75-million, unless Twitter decides to purchase an analytics company. Twitter could buy an advertising network to support the growth of Promoted Tweets. It could spend some more money on its infrastructure, which still isn’t rock-solid and will need to be expanded as more users are added. And there’s money to be spent internally on developing new features and applications.

Even so, it is hard to imagine how Twitter could spend $400-million but I’m sure there is some kind of plan, right? Then again, maybe there isn’t a plan other than taking $400-million when someone really wants to give it to you.

Right now, Twitter can pretty much do anything. The key will be moving forward decisively and aggressively to execute on the opportunity. While Twitter has received a huge boost of confidence from its investors, Twitter’s financial success is no slam-dunk given the challenges it has had creating a robust business model. So it important to remember having $400-million doesn’t fix your problems. It only puts the pressure on.

They say money can’t buy you happiness but Twitter is about to discover if it can buy success.