advantages of usb pendrive swap disputed
First of all, USB 2.0 has a practical limit of about 25 MB/sec throughput, no matter what kind of device is on the other end. Your internal hard drive can probably make at least 70 MB/sec, and nearly all modern drives can read/write faster than that.
access time is lower than traditional HD
Definitely true for "real" SSD's, but usually not for USB flash drives. Most cheaper flash chips actually have slower than HD read/write performance; high-performance SSD's achieve that by being massively interleaved so that a read or write is parallel over many chips (like RAID-0 for flash). Cheap flash drives don't do that, and often their controller is so cheap that even seek time is slower than a spinning HD (try it sometime -- take a directory of many tiny files and try to randomly read them. It'll go faster on the HD.).
avoid power on HD when is in stand-by
Um, what? Hard drives are always turned off in standby. They're a persistent storage device, so they don't need power to maintain what was written to them. *RAM* needs to stay on and be refreshed, but that's going to be true no matter what you use for swap. If your laptop isn't spinning down the hard drive when you're in sleep mode, there's something wrong with your power management software/firmware and it's not actually making it into sleep mode. (If this is happening, it's also dangerous -- spinning disks don't like being jostled, and most people put their laptops to sleep when they're going on the move.)
USB pendrives are cheaper than HD (meaning: you can't get a $5 HDD, price per gigabyte is obviously much higher for flash drives)
True you can't get a $5 HDD, but you're much better off putting your user data (pictures, documents, music, etc.) on that $5 flash drive than your swap. If you're out of space and need to free up 2 gigs for more swap space, buy the $5 flash drive, move 2 GB of your stuff onto it, then put your swap partition on the hard drive. It'll be way faster. Thetrivialstuff 17:15, 7 January 2012 (EST)