Just remember that there may be quality issues if you use cheap stores. It may be worthwhile to consider spending a little more to get better quality. There are many quality producers here on the board as well (Minleon, Advatek, Seasonal Entertainment, etc - the list of quality vendors on here is much longer than the cheap).
Most here will buy from Ray Wu's store because its DIY and cheap, quality can vary but for most in DIY this is not too much of a major issue because DIY is all about being able to do your own repairs and making up your own system.
Rays 12vdc 2811 strip is great DIY value for US$20 per 5 metre roll and shipping isnt too bad either