About a year ago, when I was looking up tens or hundreds of thousands of domain names per month, I saw this phenomenon (i.e. domains getting registered within 24 hours) happen on a such a large scale that I actually computed a statistical confidence interval to determine whether this could happen by chance. When it occurs with just 1 domain, it's annoying and suspicious. But when it happens with dozens of domains from the same person's lookups, then it's flagrant. And, of course, the confidence interval showed that it wasn't chance.
What I was doing was taking a large batch of domains and passing them through GoDaddy's bulk registration window to see which were available. Then I would spend a day analyzing them and return to buy the more promising domains -- a few hundred at a time. Whether they were really promising or not may be arguable in hindsight. But the point is, the domain bandits got them.
Later on, I made it a point to repeatedly query Whois for lousy domains -- many of which were registered the next day, I am happy to report.