The most obvious of this would be recognizing how you can programmatically hook your application with 0 users to another system with thousands to millions of users. An obvious solution that a regular marketer may recognize is simple address book integration. A less obvious solution that a hacker with API experience would recognize is how to hook into the Twitter search API, programmatically recognize hashtags and generate responses that appear legit from a real user.
Any sufficiently advanced spam is indistinguishable from content. It often takes a hacker to make the decisions that further advance field of spam to the level of content.