Stock buybacks and bumptious activist investors have been a potent cocktail for the market in the past few years - generating particularly euphoric reactions when blended for use on the same stock.

Yet Wall Street’s unenthusiastic response to activist Carl Icahn’s latest loud request for Apple Inc. (AAPL) CEO Tim Cook to repurchase shares even more voraciously suggests investors’ tolerance has risen and such tactics no longer prompt the same reliable high.

With Apple shares about flat on Thursday after Icahn's 4,600-word message of buyback-supportive bullishness. That was a relative victory in a very weak tape – but hardly the kind of reflex celebration typically triggered by Icahn’s bullish words and buyback demands on one of his big stock holdings.

More broadly, stocks of companies that are executing heavy buybacks have been trailing headline market indexes in 2014, in a sharp reversal from their status as a leading group of the past four years. 

The equity strategists at Goldman Sachs maintain baskets of stocks representing a couple of dozen dominant investment themes. So far this year, their buyback basket is lagging the Standard & Poor’s 500 index, even as the continued heavy volume of corporate repurchases are cited as one reason stocks reached new highs last month. 

And it’s become a bit less reliably profitable to tag along with activist investors on their crusades against company management. Activists - often defined as those with at least a 5% stake and a plan to agitate for strategic or financial change at a company – have become trendy and uncharacteristically vocal in recent years.

A new class of confident hedge fund managers has busily pressed for things such as spinoffs or heavy borrowing to execute aggressive buybacks.  The approach has become popular with institutional investors who view standard stock picking as a tougher game in a more efficient, no longer cheap market. By some estimates, more than $100 billion in assets are now wielded by self-styled activists. 

Yet here again, the novelty has worn off, the strategy has perhaps become a bit too crowded, and activists have had to seek out targets that might not offer as many opportunities for catalyzing change and liberating buried value.

The research service 13D Monitor – which tracks so-called 13D activist filings and campaigns – this week zeroed in on 30 ongoing activist-targeted stocks are trading well below what the activists themselves paid for their stakes. The nasty selloff in small- and mid-cap indexes has pressured many of these battleground stocks. And, of course, most of these companies were sluggish market performers or strategically hamstrung to begin with. 

Four of these names trading at a discount to the activists’ cost, incidentally, are Carl Icahn stocks, proving that he has his misses as well as big scores. They are Transocean Ltd. (RIG), Nuance Communications Inc. (NUAN), Hertz Global Holdings (HTZ) and Gannett Co. (GCI).

Other companies that drew activist interest this year and whose stocks are more than 25% below the rabble-rouser’s purchase price include Cliffs Natural Resources Inc. (CLF), Rowan CO. (RDC) and Emulex Corp. (ELX).

Ken Squire, who founded 13D Monitor, also runs a mutual fund, the 13D Activist Fund (DDDAX), which sifts among live activist situations to seek attractive values with a good chance of generating nice returns. Historically, investing in such stocks has broadly outperformed the market, and the mutual fund itself has nicely outpaced its benchmark and the S&P 500 since its founding in early 2012.

Yet this year to date it is lagging behind the S&P 500 and the S&P 400 Mid Cap 400 index (a closer fit for the portfolio).

The setbacks endured by both the buyback theme and the activist game offer at least a hint that the character of the market has changed. To a degree, both of these strategies were about plentiful liquidity and transaction-based maneuvers to lift equity values, and not as much about organic business growth. They are a microcosm of what the overall market is going through, as investors try to reconcile spotty global growth patterns with a net reduction in central-bank easy-money support.

As stock valuations have risen and financial conditions have tightened in anticipation of a marginally less generous Federal Reserve, balance sheet rejiggering holds less appeal.

This by no means is a decisive end of these games. As many stocks have dropped dramatically from their highs in the past month, bargain buybacks might start to seem smart again. And it could well be that the market shakeout is creating good value opportunities in those activist names even as their stock weakness gives the activists greater leverage. 

But it’s worth keeping a close watch on whether the liquidity-dependent modes of investing that have worked so nicely since 2009 are giving way to a new market regime.