the fundamentals greenberg cites are, for the most part correct and come to fruition; i believe SBUX is one of his notable exceptions.
however, if you go short strictly on greenberg, you can get *crushed*.
the best example - LHSP (lernout hauspie). he had this one dead to rights a few years ago on the fundamentals. it went to zero. everything he said was right. only problem? the stock went up multiple-fold (my gut says 6 or 7-fold, but could easily be wrong) after he FIRST reported the problem. and TTWO - a greenberg fave for years and years - has had lots of oscillations, but never any great stuff.
here's why:
most reporters will not report the negative side of a stock. greenberg will, after he does his own digging. so the big players who have found a stock they think is weak fundamentally will, after they've done their own research and put on a large position, call others and let them know of it. they'll put on a large position. then they give it to greenberg.
many of greenberg's stocks (which he reports on) have 10%+ short interest *already*. many have more than that. and they also often have some sort of trend or fad behind it, which the shorts 'know' will die out.
fads and trends are high risk, high reward for shorts and longs. so greenberg reports on a stock, and it takes a short term hit. smaller players jump in and short on the 'obvious' fundamental problems. momo players or individuals in love with the fad buy the dip. it breaks out again. some smaller players freak out and cover, driving it up more, which begets more people wanting to short an obvious overvalued stock, and the cycle repeats itself.
the best way to make money off greenberg? don't bail immediately on your longs. pull up a long term chart. if a long term trend is broken, THEN sell. same for initiating a short position. because at that point, fundamentals are finally overpowering the momentum players.
short term, btw, on a 'new' name, he DOES move the stock. on an old name - like a TTWO - not so much.