Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Chinese Internet company SINA (Nasdaq: SINA) exploded today, rising 15% as of this writing.

So what: It looks as if SINA and Baidu (Nasdaq: BIDU) are benefiting from investors' disappointment in Renren's (NYSE: RENN) quarterly reported last night. SINA's shares have been crushed recently, and combined with a high short interest, crazy price swings can happen without news from the company.

Now what: With the market up today and the tendency of Chinese stocks to be volatile even on quiet days, I'll chalk this up to another head-scratching move. No reason to change your investment thesis, but if you were looking to buy in it might be tempting to kick yourself today. Before you do, remember catching a falling knife is almost impossible, and this may be a sign investors are ready to jump back into this stock meaning maybe, just maybe, shares are going to stop falling. We'll see if this holds up tomorrow.

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