Suddenly, stock buybacks are all the rage. DineEquity Inc., Aecom Technology Corp. and Demand Media are among the L.A. companies that in the last two weeks have announced they’ll buy up some of their shares. They join a parade of companies nationally, all snatching up their own stock.

As the article in last week’s issue of the Business Journal pointed out, the main reason for this spate of buybacks is that stock prices have gotten so low, thanks to the market meltdown, that they represent a good buy. What’s more, if a company needs to borrow money to make the stock purchases, this is a great, low-interest era to do so. So the rush is on.

Of course, buybacks have the benefit of rewarding shareholders by supporting or even boosting the stock’s price. (Although one observer, writing last week for iStockAnalyst, made the case that recent stock buybacks didn’t do much to lift stock prices.)

Here’s the broader point: When lots of companies are buying back their own stock, it’s usually a bullish sign for the stock market and the economy in general. A surge of buybacks is a price signal, a kind of blue-light special: It means lots of managers believe their stock prices have gotten way too low relative to the improving prospects for their companies, so much so that they feel compelled to buy, and buy right now. In other words, the smart money thinks the bottom has been hit.

But I wonder. This time, it may be different. Perhaps all the stock buyback activity is not a bullish signal at all. Maybe it’s just another symptom of a sick economy.

Why? First, consider how a company with excess money would invest it in our economic environment. A business with a cache of cash could buy another company, and many are doing exactly that. But if buying another company is not an option, then what?

Well, a company could simply invest its cash somehow. But as noted, interest rates are so low they’re barely giving a pulse, and apparently they’ll stay in that near-death state for years, so interest-bearing investments are a dud. Another typical choice in normal times would be to use the cash to expand the business – and lots of expansions would be a clear signal that the economy was about to take off. But in this economy, very few companies are expanding. Indeed, many continue to hunker down.

In other words, lots of businesses are buying back their own stock not for a normal and good reason but for the abnormal reason that there’s little else to do with the money in this sour economy.

Something else to consider: Stock buyback programs are usually accompanied by brisk purchases by insiders. After all, if a company’s managers think the stock is a great buy for the company, the managers should believe it’s a good buy for them, personally, too.

But we’ve seen little insider buying in many of the buyback programs. In fact, TrimTabs Investment Research of Sausalito, which for seven years has been tracking the correlation of insider purchases during stock buyback programs, said a couple of months ago that it had never seen so few executives personally buying during their company’s buyback programs. (However, last week TrimTabs said insiders started buying more early this month.)

That means many executives, at least until recently, were saying their company’s stock is a great buy for the company. But they wouldn’t buy it themselves.

A flurry of stock buyback programs normally can be seen as a sign that the markets and the economy may be getting set to take off. Alas, perhaps not this time.

Charles Crumpley is editor of the Business Journal. He can be reached at [email protected].