Make the Nerds Geek Out
What moved the needle for PayPal in the early days is that the product made nerds geek out among each other.
Instead of taking out $5 to split lunch, they sent it over the Palm Pilot. It was so different that people would think "Wow... This is the future." Tech geeks wanted to feel like they were in the future, and it gave them that feeling. When the nerds geek out, it creates a cult-like attraction.
The idea and product of PayPal spread like wildfire. They got so much free attention. Much like Steve Jobs mastered with iPhone releases.