How many designers work at Twitter?

Right now, there are around 20 people on the design team, including our creative director, several product designers, a few interaction designers, two interns, and two design researchers. We’re growing fast, too, and looking to add another 10 or so folks in the coming months.
The @design team is a distributed team within the company, meaning nearly every designer sits with his or her team. For instance, our designers on the Clients teams sit with those engineers and PMs.
If you’d like a bit more details, feel free to email me and I’d be happy to share a bit more.
Why doesn’t the iPod Devices have a stop (■) button?

Because it is redundant. There is nothing you can accomplish with a stop button that can’t already be done using the pause, menu, next track, and/or previous track buttons.
This is not the case with media players that are physically interacting with their storage, such as VCR’s or DVD players. According to ecoustics.com [1]:
On a VHS machine, pausing the tape kept the same segment of tape rubbing against the playback drum, which if done for a long enough time could wear that spot in the tape. This could cause any number of picture and sound hiccups, or worse, cause the tape to break.
With a DVD, there’s little mechanical difference between pause and stop unless you keep it paused for more than a few minutes, after which a stopped DVD motor will spin down but a paused one will continue to run [1].
How do you map the flow of a mobile application? Can you provide examples?

I’m currently working on the IA/UX for a mobile application and as I’m mapping it out it doesn’t seem like a traditional site map makes sense nor does a flowchart. Can anyone point me to a good set of symbols that make sense …
Do designers ever do any kind of web work in Illustrator?

Yes, I only use Illustrator!
Switched over a few years ago from Photoshop and never looked back.
Why the switch? In one word, Agile. The process begs for something a bit more quick, open, and lightweight – whilst at the sometime offering great scalability to take graphics across different mediums (electronic & print). A definite must if your working towards an RIA output, there are now many plugins that output to XAML and even HTML5 – I’m currently outputting for Flex (or SWC’ing)
With the added capabilities of pixel locking and pixel preview. It makes it the perfect tool for application design. Combined with all my brand and iconography work which would be vector based anyway – everything becomes seamless.
Illustrator also offers the ability to design multiple GUIs over several artboards that can be outputted to PDF (I’ve ditched the .ai file format altogether!) This is great for quick presentations, emailing, sharing, collaborating, etc.
In fact, its changed my whole teams workflow where architects and designers all build within illustrator and develop wireframes and increment fidelity to final design in the one application. No need for Balsamiq > Omnigraffle > Photoshop round trip – just way too many file formats!
Its now got to the point where I wonder why most ‘designers’ (especially web) still use Photoshop? Quite simply, its an image retouching tool for bitmap/raster graphics. Not a design tool.
What do people think of Color’s interaction design?

This is hands-down the worst UI I’ve ever seen in an iPhone application, and I’ve seen a lot.
They seem to have done everything backwards. They’ve started from a UI that typically comes from years of usage where most of your users are power users. Normally, when you launch an application, you start with a UI tailored to people who have no clue how your application works.
When you present such a novel interface, you should do some hand-holding, especially if it isn’t self-evident. I personally don’t believe in UIs that are not self-evident, but at least provide instructions if you’re going to hide the functionality from people. They have taken a mystery meat approach to the navigation. I keep accidentally discovering new areas or functionality in the most bizarre ways.
Follow the human interface guidelines.
In an attempt to to be unnecessarily innovative, they’ve defied all of the standard navigation paradigms of the meticulously designed Apple Human Interface Guidelines (HIG). This would be fine if it was an improvement upon an already existing notion within people’s minds, but, instead, they have chosen a very abstract UI that doesn’t make sense in any world.
Those are my major complaints. The idea behind it is worth exploring, but please, please, bring the UI down to earth.