The competitors that Eventbrite started out against were the big boys - Ticketmaster, Ticketweb and individual venue and event organiser sites. As a consumer buying tickets, I couldn't see how tiny Eventbrite could end up a winner.
But Eventbrite had a better plan. They weren't trying to compete with Ticketmaster to sell Madonna tickets. They were going for a previously unserviced market - small independent events organisers. In fact I would suggest that Eventbrite in fact helped to create this market by allowing event organisers who couldn't afford large system licence fees access to a simple pay-per-ticket cloud platform, and hence the ability to run events that wouldn't have happened otherwise or to grow attendance of smaller meetups.
Eventbrite is completely free to use if you are not charging for your tickets, and they charge a percentage (which can be either deducted from your revenue or charged through to the ticket buyer, as you prefer) on paid-for tickets.
And if you fancy trying out Eventbrite - why not have a look at these lovely Tech Talkfest events :) techtalkfest.eventbrite.com