What are some examples of failed products / services which had created massive pre launch expectations through marketing and advertising?

Webvan.

The The sheer amount of online buzz generated prior to the launch of Notion Ink's Adam, was comparable to that of any technology major. It was even billed as an 'iPad Killer' receiving favorable initial reviews. But, the Bangalore based startup failed to deliver with a sub-standard product and got mired in delays. More details on the controversies here - http://en.wikipedia.org/wiki/Adam_tablet#Controversy. Excerpts: The Notion Ink Adam has been beset by a number of controversies and delays since its preorder launch in December 2010. These include shipping problems, confusion over the specifications of the machine, reportedly poor customer support and questionable build quality. The first units shipped were subject to an OTA (Over the Air) updating error in which the update file failed to completely download to the device (i.e. a product of the distribution system, not one of the content of the update), which resulted in the device becoming inoperable. As a result of communication between Notion Ink support and numerous community forum commenters, a fixed update was provided by Notion Ink to rectify the problem, in the form of an 80MB download. Many customers also questioned the gap between the quality of the screen and Notion Ink's advertised 'pure-matte glass'. The Adam also shipped without a number of promised or fully functioning applications. In late January 2011, leaked photographs supposedly taken during US Federal Communications Commission (FCC) inspections created a fresh round of criticism, with commentators remarking on the inferiority of the build to established brands, with respect in particular to hand soldered wires and components.

"Failed" being relative to hype:  Segway  In the run-up to their launch, the original PR guy (who was fired) hyped the secret product "IT" to the point that http://www.extremetech.com/extreme/72040-the-technology-behind-the-segway were speculating they were going to release a levitating scooter and more important than the Internet. On the day of the launch there were many national TV news stories with people riding Segways around talking about how walking was now obsolete. Jeff Bezos claimed that cities would be built around the Segway. http://en.wikipedia.org/wiki/Segway_Inc.#History

A classic from UK is the Sinclair C5 electric tricycle. http://www.squidoo.com/Sinclair_C5 Clive Sinclair was considered a genius of technology at the time.  Media were completely on board the hyped-up launch, and Sinclair had the funds to ensure a launch that would be noticed. But the product flopped big time.  No-one wanted to risk their lives on a slow, poorly manoeuvering, low hung 'thing' that took up too much space on narrow British roads.

http://en.wikipedia.org/wiki/Bhuvan launched by ISRO and termed as Google Earth Killer. (http://articles.timesofindia.indiatimes.com/2011-03-09/india/28671659_1_satellite-mapping-tool-google-earth-bhuvan). It turned out to be very basic application with huge number of bugs, unusable application.

The Gizmondo - http://en.m.wikipedia.org/wiki/Gizmondo Fairly incredible stuff...

I would say tata nano. They marketed it portraying the car as affordable by all both the rich and the poor. But somewhere it failed as in India car is a status symbol along with a vehicle. Many refrained themselves from buying nano thinking its a poor man's car. Others didn't buy thinking since it's cheap there must be a compromise on quality. So the idea of easy affordability failed to an extent in my opinion.

$41mm pre-launch!?