The problem with both auto-promoting after 7 days and rate limiting posts to 10 per day is that the spammer can create 100 accounts ahead of time and wait for them to auto-promote or post 10 posts per day until he reaches 50. It may stop the spam for a week, but as long as he pre-registers tons of accounts, he will eventually be able to keep spamming. It does make his job harder, at least, but it looks like he makes enough money to justify the work (I heard of $1000 off a single scam). An effective solution must involve *making account creation more difficult*.