Stocks Shaking the Investment World

There are one-hit wonders, and then there are those stocks whose initial big move is only a preview of even bigger and better gains to come.

Today, we list a pair of stocks that made some of the biggest upward moves over the past month, despite the incredible volatility in the market, which we'll pair with the ratings issued by our Motley Fool CAPS community. The higher each stock's rating, the greater CAPS members' faith in that company's ability to keep on beating the market.

Stock	1-Month �% Change	CAPS Rating (out of 5)
Tudou Holdings (Nasdaq: TUDO  )	151.3%	*
Arena Pharmaceuticals (Nasdaq: ARNA  )	67.6%	**

Source: FinViz.com; 1 Month % change from Feb. 8 to March 9.

While you were out, the markets rebounded, but they may turn tail again if Europe's fragile financial system falls apart. So before we get shaken out again, let's see why the CAPS community thinks some of these companies might continue to outperform the market.

A mighty temblor
It was the acquisition that had to be made to cement Youku.com's (Nasdaq: YOKU  ) leadership position in streaming media, but its purchase of Tudou Holdings will also shore up the gaping holes in its own operations.

With Youku owning more than one-fifth of the video market, buying the 16% share Tudou controls will give it a commanding lead over soon-to-be distant-third-place rival Sohu.com (Nasdaq: SOHU  ) . But Youku is still bleeding red ink, and even though it projects "synergistic" savings of $50 million to $60 million, such large purchases like this -- it's paying $1.1 billion for Tudou -- often create more indigestion than they're worth.

When the deal was announced, I closed out my outperform rating on Youku and switched it to an underperform. I'll be maintaining that outlook, as I think this acquisition will weigh it down even further. More than half of the CAPS members rating Youku apparently agree with me (or me with them), and the bounce Tudou shareholders got from the offer should entice them to take the money and run.

But tell me in the comments section below whether you think this will be a successful pairing in the long run, then add Tudou and Youku to�your Watchlist�to see how it plays out.

Overweighting expectations
I've mocked the weight-loss therapies being developed by Arena Pharmaceuticals, VIVUS (Nasdaq: VVUS  ) , and Orexigen Therapeutics as nirvana for couch potatoes like me. With the potential for VIVUS' Qnexa in particular to actually receive FDA approval, we'll be able to still sit back and pop bonbons while avoiding what's really needed: a healthy diet and exercise.

But as ATLnsider recently noted, the treatments aren't really designed or intended to work like that. Since they're being developed for the obese, doctors are going to insist on permanent lifestyle alterations that ensure the patient is doing more than thinking a pill is going to cure his or her ills.

Qnexa is not intended to replace diet and exercise. Qnexa is intended to be used in conjunction with diet and exercise. Qnexa will not work without a proper diet and regular exercise. No reputable doctor should ever prescribe Qnexa without requiring their patients to adhere to significant permanent lifestyle changes, including regular exercise and a healthy diet that will support and contribute to weight loss.

Agreed, but I still maintain that the weighty assumptions investors are extrapolating to Arena's lorcaserin from Qnexa's pending approval are overdone. The approval of one does not automatically mean the other will follow. Yet with 91% of the CAPS members rating Arena to outperform the market averages, it's clear I'm in the minority, though its low, two-star CAPS rating suggests they think there are better places for your money.

Add the biotech to the Fool's free portfolio tracker and tell us on the Arena Pharmaceuticals CAPS page whether you think it will be able to continue its climb higher regardless of the outcome.

Shake, rattle, and roll
These two stocks shook the market this past month, but the Fool has found one company that's digging up massive profits and is likely to continue to do so if the markets become rattled. Roll on over to get your free copy, but hurry, because it's available only for a limited time.