Very few of the Windows Phone 7 & 7.5 devices like the Samsung Focus, the Dell Venue Pro had a MicroSD slot. Microsoft’s primary focus was on Flash storage that’s easier to manage & faster. But, the devices that had a MicroSD slot had expandable storage. But, the way expandable storage works on Windows Phone 7/7.5 is different from other platforms. Say, you got a Samsung Focus. It has 8 GB of internal storage & you want to expand it. When you insert a MicroSD card, the phone resets. This means that you have to insert a MicroSD when you get your device & if you decide that you want to expand it months later, you reset your phone. Of course, your data is backed up on your PC via Zune & your contacts are backed up in the cloud. Also, there’s no hot swapping of MicroSD cards. You can’t put movies on the card & insert it in your phone when you’re going on a trip. In short, MicroSD storage “integrates” with internal storage.
With Windows Phone 8, Microsoft is bringing removable MicroSD support to their mobile platform. What this means is you can insert a MicroSD card months after you buy a device & you can even hot-swap MicroSD cards like you’re probably used to. It will have support for Photos, Music, Videos as well as Installing apps (we don’t know much about how this will work, as of now). Also, Flash storage is, considerably, expensive. So, devices with small amounts of internal memory with an expandable microSD slot would be manufactured to reduce costs as well as satisfy the consumer storage demand. Microsoft says, “These will help Windows Phone scale up and down.”