In a sign that Apple's stronghold over the tablet market is finally loosening, the company's share of the tablet market dropped 16 percent in the last quarter alone, according to research firm IDC.

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IDC's report shows Apple's 66 percent share fell to 50 percent from the prior three-month period while demand for competing devices from Amazon and Samsung surged.

Worldwide tablet shipments totaled 27.8 million in the period, 50 percent higher than a year earlier, IDC said in a report released Nov. 5. Samsung shipped 5.1 million devices in the third quarter, more than double the number it sold in the previous period, and Amazon's market share increased to 9 percent from 4.8 percent.

According to the report, Apple lost its share due to consumers putting off iPad purchases as they waited for the hyped release of a new model, the iPad mini, which went on sale Nov. 2 with Wi-Fi only versions.

"A sizeable percentage of consumers interested in buying an Apple tablet sat out the third quarter in anticipation of an announcement about the new iPad mini," Tom Mainelli, research director for tablets at IDC, said in the report. "Now that the new mini, and a fourth-generation full-sized iPad, are both shipping we expect Apple to have a very good quarter. However, we believe the mini's relatively high $329 starting price leaves plenty of room for Android vendors to build upon the success they achieved in the third quarter."

Apple's loosening grip over the tablet sector could help explain the recent abrupt firing of some of its executive staff members, including the head of its iOS mobile software group, Scott Forstall. The company could be worried its lost its edge over its rivals.

Forstall is rumored to have quit the company regarding the much beleaguered Apple Maps on iOS6. Numerous sites claim to have spoken to unnamed sources that allege Forstall refused to sign an apology concerning Maps' failure. Forstall will be an adviser to Chief Executive Tim Cook until he leaves the company next year.

"Forstall was a close protege of and possible successor to Steve Jobs before Cook's ascendancy," according to The Seattle Times.

As The Times notes, a BusinessWeek profile in 2011 called Forstall "the sorceror's apprentice" and said he "may be the best remaining proxy for the voice of Steve Jobs, the person most likely to channel the departed co-founder's exacting vision for how technology should work."

The story noted that Forstall is named on about 50 Apple patents, including a key one in 2009 that named him, Jobs and other employees as co-inventors of a touchscreen device controlled by finger commands.

Amazon poised for success with Kindle Fire HD?

Amazon's third quarter market share was 9 percent, up from 4.8 percent in the second quarter, surging because the company's new Kindle Fire HD tablet began shipping. And those shipments were only in the U.S. As Amazon starts shipping the 8.9-inch Kindle Fire in November, it'll have a diverse lineup of tablets.

"It's highly likely that Amazon's market share will go double digits---say 12 percent to 15 percent," according to tech site ZDNet.

Things could really begin to snowball when Amazon's Kindle Fire begins shipping internationally. Amazon's market reach is limited when compared to Apple, but the company will have enough distribution to gain share of the market.

Amazon also has a readymade system to promote its new tablet. The retailer can use its home page, its customer lists, and recommendations to push the Kindle Fire HD. The company can also take advantage of the iPad mini's price tag of $329. Amazon can still easily play with lower pricing and balance that against quality features and services.