Economy

If you think of Amazon.com (Nasdaq: AMZN)as nothing but an online retailer, think again. The house that Jeff Bezos built is very serious about treating its computing services like a real business.

Margins matter. The more Cabot Microelectronics (Nasdaq: CCMP) keeps of each buck it earns in revenue, the more money it has to invest in growth, fund new strategic plans, or (gasp!) distribute to shareholders. Healthy margins often separate pretenders from the best stocks in the market. That's why I check on my holdings' margins at least once a quarter. I'm looking for the absolute numbers, comparisons to sector peers and competitors, and any trend that may tell me how strong Cabot Microelectronics' competitive position could be.

 SINA (Nasdaq: SINA) is still growing, as long as you only focus on the new media darling's online advertising business. Revenue in its latest quarter climbed 12% to $108.2 million, with brisk growth in the company's Web-based advertising business more than offsetting weakness everywhere else. Adjusted earnings climbed 65% to $0.50 a share.

Among bearish investors, these are the three words most often used to describe Rackspace Hosting (NYSE: RAX). But are they fair? I'm not buying it. With each passing quarter, the company gets better at squeezing revenue and profit out of its burgeoning digital fiefdom.