Ken Parish gives a generally approving link to a piece of junk science claiming that bans on DDT inspired by Rachel Carson’s Silent Spring have caused the deaths of millions of third world residents. He also gives a link to a more balanced piece which gives cautious support to limited use of DDT in anti-malaria campaigns in poor countries (the only use that is currently legal, although there is widespread illegal use as an agricultural insecticide). While noting that not all of Carson’s 1962 claims about the dangers of DDT have stood up to subsequent scrutiny, the author dismisses right-wing conspiracy theories like those in the first link, and makes the point that Carson was campaigning against the use of DDT as a broad-spectrum insecticide, not as an anti-malarial. As the author notes
Soaking the biota in DDT like it was bubble bath, standard practice at the time Silent Spring was written, was a bad thing and Carson was right to condemn it.
As this piece makes clear, the main reason for the abandonment of DDT as the core component in anti-malaria campaigns was the growth of resistance, which was of course exacerbated by indiscriminate use. The ban on DDT use in developed countries, to the extent it had any effect, slowed the general rise of resistant species, and therefore increased the effectiveness of DDT in its anti-malarial use.
The main advantage of DDT is that it is cheap and persistent. Persistence is also one of the main disadvantages, along with broad-spectrum effects. For poor countries, and for the specific purpose of anti-malaria campaigns, the benefits arguably outweigh the costs, and this is why DDT continues to be used in these countries.
The question of when the extra cost of alternative pesticides is sufficiently small to justify abandoning DDT, or sufficiently large to justify readopting it in countries that have abandoned it, is an important one that needs careful analysis. The cause of rational debate is not assisted by propaganda pieces like the one Ken cited.
Note This version has been edited in response to points made by Ken in the comments thread.