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 hydrogen fuel cell maker Plug Power (NASDAQ:PLUG) jumped again today after an analyst made positive remarks about the company. The stock spiked as much as 11%, but a sell-off at midday brought shares down to a 2% gain in late trading.

So what: Roth Capital said on Friday that after meeting with Plug Power CEO Andrew Marsh it was more confident the company can meet its 2014 revenue and booking guidance. Analysts expect $73.8 million in revenue in 2014; the company reported $5.6 million in revenue for the first quarter, so growth has to pick up quick.  

Now what: While Roth Capital had positive things to say about Plug Power's operations, it didn't get bullish on the stock because of its high valuation. Shares are trading for about 12.5 times estimated 2014 sales and the company is still expected to report a loss for the year. That's too high a price for me to pay -- I'll wait for a profitable turn and a lower valuation before even thinking about jumping in.