As a rule of thumb, never take investment advice from a hedge fund manager who posts his predictions on Twitter.

On Thursday morning, BAM Investor’s J.G. Savoldi used the microblogging service (and a follow-up press release) to warn investors that Apple (AAPL) was about to crash and could hit $45 a share — perhaps as early as this fall.

But instead of going down, the stock went up. With an hour of Savoldi’s tweet, Apple hit a new intraday high of $272.90 a share. On Friday, it climbed some more, reaching $275 and closing at a record $274.07 — within spitting distance of a quarter trillion dollar market cap.

Savoldi’s prediction, of course, was nothing but a shameless publicity stunt. Almost anything can happen in the stock market, but Apple’s shares selling for less than the company’s $42 billion holdings in cash and marketable securities is not one of them.

But this is the kind of thing we see whenever Apple makes too much news. In May it announced that it had sold 2 million iPads. In early June, Steve Jobs introduced a new iPhone and on Tuesday the company pre-sold a record 600,000 of them — despite a rush of pre-orders that overwhelmed its servers. Next Thursday, as sure the sun comes up, there will be lines at stores wherever the phones are sold. Three days later, Apple will close the books on what’s looking very much like another record quarter.

Yet despite all this — in fact, because of all this — Apple is a ripe target for the talking heads on cable business news. Want to see what that looks like? Check out the line of questioning on Friday’s episode of CNBC’s Power Lunch in an episode entitled “Apple On Top, Time To Worry?” The video is available here and copied below the fold.

[vodpod id=Video.3863631&w=5005&h=350&fv=]

Kudos, by the way, to CNET’s Tom Krazit for holding his ground.

See also:

• The Apple-to-$45 guy strikes again
• Analysts scramble to raise AAPL targets
• Apple hits a new all-time high

[Follow Philip Elmer-DeWitt on Twitter @philiped]