Name-brand memory cards are a safe bet for getting a quality memory card.
Not all SD Cards are the same. Many are "get what you pay for" from bargain sites, where cards are reconditioned or out-right hacked to fake their capacity.
That's why we've brought in SanDisk memory cards from a North American supplier for our accessories needing SD card storage. It's a tidy little package, complete with the microSDHC card, SD-card adapter, and plastic case.
Our latest tests under Linux with a USB2 SD card adapter show an hdparm -t results of:
Not willing to just trust anything we read, we put a card through the "Gold Standard Tester" on a USB2 hub, H2testw v1.4, which reported:
Test finished without errors. You can now delete the test files *.h2w or verify them again. Writing speed: 5.95 MByte/s Reading speed: 18.6 MByte/s H2testw v1.4
In short, we're pretty happy with the results of these cards!