The comment below was plucked from this web sites comment section, I thought it was interesting. Some of the other comments are interesting also.

"it's Samsung's "fault". They built a device that wasn't in the WP7 hardware specifications. WP7 wasn't ever intended to have expandable memory. That said, MS didn't reject the device. Samsung was either trying to one-up the WP7 competition by sneaking an extra "killer" feature that backfired on them or they were planning ahead to make this phone future proof in the expectation that expandable memory down the road. MS apparently decided to let that go and started developing WP7 to include this option but wasn't able to fully test it.

Who's the bad guy? I say no one. The phone is fine and can be used without the SD card. No one paid a premium for that option and it wasn't ever promoted. The only people that got burned were those that tried modding their phones. Samsung was being ambitions and MS was being inclusive. Would WP7 be better without the Focus? No. Would the Focus be better without the SD slot? No."

http://www.engadget.com/2011/04/15/windows-phone-7-certified-microsd-cards-emerge-at-atandt-stores/

.at15t_email { background-position: 0px -4120px; }

Cellphones, Peripherals, Mobile Peripherals

Windows Phone 7-certified microSD cards emerge at AT&T stores: $32 for 8GB

By Darren Murph posted Apr 15th 2011 4:01PM

Exclusive

Well, well -- what have we here? For avid users of Windows Phone 7, you no doubt remember the hubbub last year surrounding the so-called difficulties with Microsoft's latest and greatest mobile OS accepting microSD cards. We'd been pounded with news of "WP7 certified microSD cards," but even now, they're more ghost than reality. That said, it looks as if the tables are turning, with an nondescript AT&T store grabbing fresh stock of "certified" 8GB Class 4 microSDHC cards. Based on the packaging, it's fairly clear that Microsoft's taking the lead here, but SanDisk has been knighted to provide the hardware. $32 will soon get you a card that doesn't destroy itself upon insertion in your Samsung Focus, and we're guessing that they'll be available to purchase sooner rather than later. So, you sizing up, or what?