Pneumonia is quite common in people who are bedridden or immobile as Mr. Nicklinson indeed was and often results in death.
Readers may recall an Australian man, Christian Rossiter, a quadriplegic who went to court a few years ago asking that, if his feeding tubes were removed, that his care facility would not reinsert them once he became unconscious. Rossiter won his case but did not proceed with his expected actions. Instead, like Nicklinson, he also contracted pneumonia and died.
(Note: Their court cases were about different issues; Rossiter's was not about euthanasia)
Some commentators have observed that Nicklinson's commitment to the British High Court proceedings that were eventually unsuccessful were a sign of someone with incredible courage and determination. Likewise, Mr. Rossiter. No one questions that their lives were changed dramatically through their conditions. No one doubts that this would have been very difficult to cope with - including for family members.
Both men are and should be remembered for their courage. Unfortunately, Mr. Nicklinson at least will likely also be remembered, at least emblematically, whenever someone mentions 'Locked-In Syndrome'. While this is a terrible affliction we need to remember that not everyone who has it wants to die rather than live.