Tell that to Rajiv Gandhi
The Tamil Tigers have used that tactic for almost 15 years to great effect.
Interestingly enough, there may even be a North Korean connection to some of the Tamil attacks, and perhaps a Taliban connection, too. Of course, the Tamils aren't the only ones that use the suicide tactic. According to this source, as of June, 2001, suicide terrorism had been used by 15 different terrorist groups in 12 different countries.