had the same issues selling the 'sti' a few months back:

*people sms asking for personal email address 'as they thought its an easier way to contact me'

*SMS from non australia mobile numbers

*get an sms saying will pay $2x,xxx for the car, call back the number few minutes later. Person ask what car are you selling, proceed to tell them the car and then they said nar i'll pass?

there are plenty of interesting scammers out there, nothing beats getting a bank cheque / going down to the bank with the potential buyer to transfer the funds.