Distro for a startup?

I don't think you'd find a general standard answer to this question. The truth is only you know the answer to it.

Some random points to take into consideration:

Avoid exotic distributions

There are solid distros around (debian, centos, opensuse, ubuntu, fedora, ...) to chose from. No need to consider getting your own LFS or something like Gobolinux. Not only are mainstream distributions more field tested, but they're also easier to get help for.

What's on your server?

It may be easier to get the same distro (or a close relative debian-ubuntu, centos-fedora, ...) to your work stations. Can you imagine an incompatibility between developer's env and production server?

Ask your developers

No need to impose a distro that is "better" if none of your programmers know how to use it. Ask them for an opinion, it'd be far more accurate.

Consider paid support

Sometimes, even the most skilled linux guru doesn't have the time to support dozens of workstations. Canonical, Red Hat, and so many others, offer paid support. Even though it seems expensive, delegating support to 3rd party will allow you to focus on your core business, what you do best.

Avoid Rolling Releases

This is a small variation of the first point. There's nothing worse than supporting a version-less product. Arch Linux, Sabayon, Gentoo are great distributions, but since they lack proper versioning, it's very easy to get lost. Remember, if you're asking this question here, you're probably looking to unify the working environment of your developers. Versions are a must.

Read up on the specifics

Your business probably relies on some specific packages (like PHP, MySQL, git, memcached, ...). Browse the documentation of existing distro looking for common/known issues before adopting it.

While SELinux is a good option for a highly sensitive environment, it will require skilled admins and may not be appropriate for a start up as you will find you need to remove controls.

So a more standard distro will be easier to maintain.

Debian, CentOs or Ubuntu would be just fine- they can all be secured appropriately, have active development and maintenance and are easily usable.