I formatted my Sandisk Cruzer Contour 4GB, and found the speed of writing dropped to 15MB/s. After I googled but found no solution to this, I got following approach by chance:
Find your usbdisk in “(RC)My Computer-Manage-Disk Management”, format it with “File System”: “Fat32″, “Allocation unit size”: 512. and that’s all! Let’s see it in ATTO Disk Benchmark:
The first pic is the test once I got the usbdisk, and the second one is the data after my purposed approach. Hope it will help you out 
之前出于对U3的失望，将Sandisk Cruzer Contour U盘自带的U3删掉了，结果使用发现U盘的写入速度明显下降，由原来的18MB/s 降到了不到15MB/s 。多番查找资料未找到解决办法，决定自己研究。幸找个一个方法，跟大家分享一下：
在(右键)我的电脑-管理-磁盘管理中找到你的U盘，选中进行格式化，参数选择：Fat32，512。完成！现在看一下结果吧：
第一个图是刚到手时的数据（原装），第二个图图是采用这个方法后的数据，基本一致。希望这个方法能够帮到跟我一样的可怜同学^ ^
