Fast forward to the Web. When we go to eBay, we want our bids and product descriptions to be accurate. Airlines and service industries want the correct hotel rooms or flights, billed at the right price to the right customer. News outlets want to make sure that an item is not subtly changed to alter its meaning. Part of the reason is that vendors have yet to create decent tools and make them readily available to customers.
Integrity checkers address many security needs.
They can detect accidental system and file corruption early, preventing additional damage as errors compound themselves. They can protect against viruses by looking at file and system behavior rather than static signatures. By their very nature, viruses cause integrity violations. Web sites are the most visible and vulnerable targets of integrity attacks - most of which are easily preventable. Integrity checkers are well worth the investment.