Stocks to Buy, or Sell? Take Your Money and Run from these Huge Gainers

If you felt a shiver Wednesday afternoon as the stock market closed, it was Sam "The Grave Dancer" Zell walking over your portfolio.

Zell is a noted real estate investor who visited CNBC last week. He told viewers that the stock market was starting to remind him of the housing market back in 2006. No matter what happened economically or politically prices just kept going up every day, every week and every month to levels that no longer made sense.

Zell has made his billions by buying in times of distress and selling in times of irrationally high asset prices. He once commented on his nickname saying that he dances with the skeletons of other people's mistakes.

As the market appears to be at higher risk, it is more important than ever to not become one of the skeletons that enriches Zell and other sophisticated investors.

Zell's suggestion that stock prices are overheated make it time to examine some of your holdings, and figure out which ones are steadily climbing – and which ones have had a good run that's ending. It might be a good time to harvest profits from the market's strong upward move.

This is particularly true of consumer-oriented names, as there are a lot of reasons consumers could tighten up the purse strings in 2013.

Here are two of the year's biggest gainers, that might look like stocks to buy based on 2013 performance – but look unlikely to maintain their share prices. They're just like the kind of "skeletons" Zell was referring.

No Longer Stocks to Buy: Take Your Gains in these Two Names

One of the best performing stocks so far this year is consumer electronics giant Best Buy Co. Inc. (NYSE: BBY). Much of the increase in the stock was initially associated with rumors that the founder would partner with a private equity firm to take the company private. No bid materialized by the deadline, and this now looks unlikely.

In spite of beating analysts' estimates by a small margin, the company is still not performing well. Sales are projected to continue to decline over the next two years. Best Buy has an enormous amount of store and employee cost dedicated to an industry that is transforming into a primarily online industry.

In order to stay competitive the company will have to lower prices to the point already-thin profit margins disappear. If you have been lucky enough to enjoy the more-than 100% price jump this year, it is a good idea to take your profits before reality drives the stock price down over the next few months.

NetFlix Inc. (Nasdaq: NFLX) is another stock that has seen extraordinary gains this year and could take a dramatic tumble should the stock market reverse direction. What a nice stock to buy six months ago when it was trading around $92, only to hit nearly $200 in February.

The stock jumped ahead following the fourth-quarter earnings release. Earnings surpassed expectations and subscriber counts advanced but the actual numbers were far below the year ago levels. It has gained 87% in 2013.

This company is doing a lot of things right, such as developing original content and expanding internationally, but this is a competitive business and all the good news appears to be reflected in the current stock price.

Netflix trades at more than 500 times earnings and is at almost 60 times the optimist analyst estimates for 2013. Should it fall short of analysts' expectations, or we endure a broader market tumble, this stock could easily give up its 2013 gains. If you have ridden the stock higher, it's probably time to step off the train before it reverses direction.

For more stocks to buy – not sell – check out this report: 5 Picks Buffett and Insiders Love Right Now