There are so many people working for each company, consulting for them, advising them, and attending their investor pitches, that I suspect it is hard to keep secrets. It is like that in any industry.
I've had someone attend an investment pitch who I'm pretty sure then told a potential competitor exactly what I planned on doing. If this happens to my company, which is pretty insignificant compared to Lyft and Uber, I bet it is even worse for them.
Leaks are a reasonable explanation, but it's probably worth remembering they're not the only one. When you've got reasonably smart people working on solving problems and developing products/services in the same space, a certain amount of convergence is going to be natural.
I don't work for either and this is one of several ideas I considered while thinking about that space, and everybody here has probably had the experience of watching a startup build something around an idea they had but never really shared.
It sorta looks like Lyft pushed this out ahead of schedule based on Uber's announcement. The website says it's SF-only and iPhone-only.
Which, if so, is a great testament to their ability to respond quickly. And also, as a user of these services, I love the competitive pressure they're putting on each other.
I've had someone attend an investment pitch who I'm pretty sure then told a potential competitor exactly what I planned on doing. If this happens to my company, which is pretty insignificant compared to Lyft and Uber, I bet it is even worse for them.