The difficulty in determining what the Koran has to say about virgins and such is establishing what the Koran says, period. Translators vary widely in their rendering of the spare and often opaque text.

Muslims are motivated to terrorism because the Koran, the Bible of Islam, tells them that fighting non-believers is a duty of every Muslim and the only way to be certain of going to heaven is to die fighting in the cause of allah.

What 72 virgins?

According to this page, the specific Hadith in which the number of virgins is specified is Hadith Al-Tirmidhi in the Book of Sunah (volume IV, chapters on The Features of Paradise as described by the Messenger of Allah, chapter 21, About the Smallest Reward for the People of Paradise. The same hadith is also quoted by Ibn Kathir in his Koranic commentary (Tafsir) of Surah Al-Rahman:

"The Prophet Muhammad was heard saying: 'The smallest reward for the people of paradise is an abode where there are 80,000 servants and 72 wives, over which stands a dome decorated with pearls, aquamarine, and ruby, as wide as the distance from Al-Jabiyah [a Damascus suburb] to Sana'a [Yemen]."

"Verily, for the Muttaqun [righteous], there will be a success (paradise); gardens and grapeyards; and young full-breasted (mature) maidens of equal age; and a full cup (of wine)" (An-Naba 78:31-34).

Most other English translations, both on-line and in print, replace "full-breasted maidens" with some tame construction such as "companions." Inquiring further, we find that the Arabic word at issue is WakawaAAiba, which appears nowhere else in the Koran. The French, less prudish in these matters, usually render it as something like des belles aux seins arrondis, "beautiful women with round breasts," so I think it's pretty clear what the Prophet, or at least his stenographers, had in mind.

So nothing in the Koran specifically states that the faithful are allotted 72 virgins apiece.

If they can make it to heaven, one of the rewards all Muslims are promised is 72 virgins. The number of virgins is not specified in Koran, it comes from a quotation of Muhammad recorded in one of the lesser known Hadith. ("Hadith" is an Arabic word meaning traditions. After Muhammad's death, several collections of his deeds and sayings were assembled. These collections are called Hadith and form the second most authoritative document is Islam, right after the Koran.)

So it isn't the case that only martyrs get the virgins, but the only way to get the virgins is to get to heaven, and Koran is quite specific that the only way to be certain of getting to heaven is to die in Jihad.

On being a martyr

Often Islamic spokesmen use the martyr (shahid) and not suicide bomber, since those who blow themselves up almost daily in Israel and those who died on September 11 were dying in the noblest of all causes, Jihad, which is an incumbent religious duty, established in the Koran and in the Traditions as a divine institution, and enjoined for the purpose of advancing Islam. While suicide is forbidden, martyrdom is everywhere praised, welcomed, and urged: "By the Being in Whose Hand is my life, I love that I should be killed in the way of Allah; then I should be brought back to life and be killed again in His way..."; "The Prophet said, 'Nobody who enters Paradise will ever like to return to this world even if he were offered everything, except the martyr who will desire to return to this world and be killed 10 times for the sake of the great honor that has been bestowed upon him'." [Sahih Muslim, chapters 781, 782, The Merit of Jihad and the Merit of Martyrdom.]