When OnePlus released its first phone back in 2014, it pulled off an interesting publicity stunt. Buyers could only order its One phone if they obtained an invitation first. OnePlus is finished with this invite system for the moment, and it's come up with a clever new idea to replace it: send the company money, and it'll send you a phone back.
To the company's credit, the invite tactic drummed up some free publicity and made the phone sound like an exclusive piece of hardware, sometimes drawing Apple-esque street queues at stores. That system got old pretty quick, though. During subsequent sales of the One phone and its successor, the OnePlus 2, the overall reaction to the order-by-invite method was more "again? Come on!" than "heh, that's cute." The prospect of needing a password, a secret handshake, and a decoder ring to offer some dollars to a company in exchange for a smartphone didn't have the same pizzazz as it did before.
OnePlus previously said it was selling phones by invitation due to supply constraints. The company gave no reason why it's now decided to do business the old-fashioned way, though, nor has it promised that the invite system is gone for good.