Sell Block

Team player that he is, Cramer is dissecting the most popular stocks in the CNBC Million Dollar Portfolio Challenge for today's Sell Block. Going through the top ten stocks that people have been picking in the game – he can only talk about seven of them because of size restrictions – Cramer is finding that they're all speculative, single-digit stocks. Now, Cramer is an advocate of speculation, but only if the homework's done and it's the right fit for your goals. He's all for buying these little risky stocks that could deliver big upsides, but he never recommends speculating with more than a fifth of your portfolio and wants you to remember that with great risk comes great responsibility. In a game like the Portfolio Challenge, people can take these huge risks because they aren't playing with real money, and that's why these speculative plays are so popular. But the market isn't a game, Cramer says, and treating it that way could get you into the House of Pain pretty easily.

Of the seven most popular stocks in the Portfolio Challenge, Cramer's only bullish on one: Charter Communications , a cable company he's been behind for a while. The cable business is on fire, he says, and Charter is up more than 15% since he last recommended it on April 10. Charter has a good debt refinancing angle and it's undervalued based on what Comcast has been willing to pay for other cable companies, Cramer says.

There's another stock – Sirius – that Cramer would neither buy nor sell. He thinks it's a winner regardless of whether the XM merger goes through, but if it doesn't there will be a ton of bloodletting. It's too cheap to sell and there isn't enough conviction to buy, he says.

The rest of the bunch is in the sell block. CMGI is on the list; a company that Cramer says has changed its business model enough times to make his head spin. It is currently incarnated as a supply chain and logistics company, but Cramer wouldn't be surprised if that changed tomorrow.

Oilsands Quest, is levered to natural gas and crude oil in Canada, but Cramer would rather you be in deep water drilling than Canadian energy plays.

Then there's Crystallex , a gold mine in Venezuela that exists perpetually in a state of crisis, Cramer says, because of the political instability in that country.

Fremont General is another contest favorite, despite all its subprime exposure. Cramer likes the financials, but there are better plays than Fremont, he says – most notably Annaly Mortgage or Downey Financial , which he recommended right here yesterday. You don't have to go with the smallest market-cap, lowest priced stock in real life, Cramer says. You go with best of breed.

And last but not least, Cramer has noticed that a little stock by the name of Vonage is appearing all over the place. He says there are no circumstances under which it's OK to own, or pretend to own, Vonage the dog.

Bottom line: Cramer hates to spoil the fun, but he wants you to remember that the CNBC Portfolio Challenge is only a game. He wants you to be careful - the stocks a lot of people have been favoring in the contest are not stocks he would recommend buying with real money. Cramer likes Charter and Sirius is a don't buy, but CMGI, Oilsands, Crystallex, Vonage and Fremont General are all stocks he says you should consider selling.

Questions? Comments?