The two main reasons people go to ebay for laser pointers is cos of convenience and low prices.
In the end you normally end up out of pocket and don't even have a laser to show for it.
Lasers are missing IR filters which makes them dangerous and gives exagerated power readings. The lasers are also often pot modded (power is boosted) which makes the lasers unstable and likely to burn out.
Unless you are buying from a seller with an established rep, stay away from ebay.
An excellent alternative is Dragonlasers at
www.dragonlasers.com
Their prices are pretty much as low as you can get for a genuine high quality laser pointer and they have outstanding customer service.
They even sell lasers that have no duty cycle and an on/off switch which makes then ideal for mounting on a telescope
http://dragonlasers.com/hulk