What is the place of viruses in the ecosystem?

What is the biological purpose of viruses (other than to make living things miserable)? Do they have any beneficial purpose whatsoever, like some bacteria do? Are they a part of the ecosystem, like bacteria are? Do any living things feed on them (for instance, you could say mosquitos are parasites, but bats eat them)? If viruses aren't part of the ecosystem, and serve no beneficial purpose, can we completely eradicate them? What's stopping us? The fear that some will survive and mutate into super viruses? I understand that there will be a few people out there who will say "population control" (both in people and other living things) but don't we already have enough other factors causing death in living things like other diseases, pollution, war, accidents, loss of animals' habitat, etc? How did viruses originate? Scientific viewpoints only, please--I am really curious. If anyone has some latest research articles to share please post.