> Bot retweets tend to cascade, too
There's a reason for that. Twitter offers an API to get a massive stream of tweets. They used to provide it in various sizes, leading up to what was called the "firehose". Now they only have a streaming API with filtering (but gets a very small, but constant random sample of tweets), and the "firehose", which is all of them -- and you have to pay for it through a third party partnered with Twitter. When you're doing large-scale datamining, the firehose can be invaluable, albeit expensive (Depends, but is anywhere between $300-$6000/month). But bot makers don't always have that kind of scratch, so they will just consume the public API, which is generally good enough.