Stocks have just put in their best first-half performance since 1998, with the S&P 500 (SNPINDEX:^GSPC) and the narrower, price-weighted Dow Jones Industrial Average (DJINDICES:^DJI) adding 12.6% and 13.8% (price return), respectively.

Let's take a quick look at this week's two most popular stocks. When I say "popular," I don't mean the ones that performed best, but those that popped up on investors' radars -- for good or bad reasons. Here, then, is who made a splash.

Noodles & Company (NASDAQ:NDLS)
Thursday evening, on the eve of the initial public offering of fast-casual dining chain Noodles & Company, I wrote:

Foolish investors know that IPOs are a beauty contest and are, as a result, skeptical of the "value proposition." At the $16 midpoint of the new pricing range, shares of Noodles & Company would be valued at 52 times trailing normalized earnings per share, or 31 times tangible book value per share. In this case, that skepticism looks richly deserved.

That didn't stop underwriters from pricing the shares at $18, or $1 above the top end of a $15 to $17 pricing range that had already been raised once. That, however, was nothing compared with what transpired once the shares hit the secondary market, as the shares opened at $32; by the end of the session, they settled at $36.75 -- better than a double with respect to the IPO price.

That's a wonderful result for investors who were able to obtain an allocation of shares as part of the IPO. For the company itself, however, it ought to be disappointing. Why? Consider what actually occurred: It sold shares at a price that the market immediately judged was equal to just half their intrinsic value -- in other words, the company appears to have left a lot of money on the table.

Mind you, it's legitimate to ask whether the market has made a rational assessment of the shares' intrinsic value, which it now pegs at 118 times trailing normalized normalized earnings per share and 73 times tangible book value per share. This was a small IPO (Noodles raised less than $100 million), and decent investor interest can have a big impact on price under those conditions. This could well be a situation in which liquidity trumped valuation discipline.

BlackBerry (NASDAQ:BBRY)
Shares of BlackBerry fell by more than a quarter on Friday, as the company disappointed with the results of its fiscal first-quarter ended June 1. The magnitude of the stock's loss hints at the magnitude of the negative surprise, and, indeed, the company lost $0.06 per share (excluding one-time items) where analysts had been expecting a $0.13-per-share profit.

The company is struggling for oxygen in a market increasingly dominated by Apple's iPhone and devices running on Google's Android operating system. Friday's report provided little to no evidence that the company is having (or would have) any success swimming against that tide; BlackBerry didn't provide unit shipment numbers for the Q10 or the Z10, the newly launched products under its new BlackBerry 10 iteration.

Shares of BlackBerry look cheap on a number of metrics (they're trading at less than their tangible book value, for example), but I'd caution investors that this is a speculative situation, not an investment operation; "cheap" stocks of companies battling for survival can easily get a lot cheaper.

Fool contributor Alex Dumortier, CFA, has no position in any stocks mentioned; you can follow him on LinkedIn.

The Motley Fool recommends and owns shares of Apple and Google. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.