How Reliable Are Gartener Predictions of Future?

http://gartner.com/it/page.jsp?id=593207

Gartner Predictions [not my predictions, but a couple overlap with what I believe]:
Gartner, Inc. has highlighted 10 key predictions of events and developments that will affect IT and business in 2008 and beyond. Here I list a few that I found interesting and in general agree with.

Through 2011, the number of 3-D printers in homes and businesses will grow 100-fold over 2006 levels. Printers priced less than $10,000 have been announced for 2008, opening up the personal and hobbyist markets.

I have been following the rapid prototyping and rapid manufacturing industry for several years. I have noted the falling prices, increasing capabilty and increasing popularity of the various 3D printers back in October 2007

The Desktop Factory 3D printer $4995 will be available in 2008. Their goal by 2011 is to have their 3D printer below $1000.
1. sales of hundreds of units in 2008 to a plan of 3500 in 2009.
2. In 2010, a price point of roughly $2,000 and somewhere between 20,000 – 30,000 units.
3. In 2011, with a price below $1000 and enter the consumer space. They believe they will sell over a 100,000 units a year

By 2011, Apple will double its U.S. and Western Europe unit market share in Computers. Apple's gains in computer market share reflect as much on the failures of the rest of the industry as on Apple's success.

I had covered the likely increase in Apple's market share January 2008

By 2012, 80 per cent of all commercial software will include elements of open-source technology

By 2011, early technology adopters will forgo capital expenditures and instead purchase 40 per cent of their IT infrastructure as a service.

By 2010, 75 per cent of organisations will use full life cycle energy and CO2 footprint as mandatory PC hardware buying criteria.

http://nextbigfuture.com/2008/02/reviewing-my-predictions-on-future-and.html