What is the advantage for the registrars that are holding on to the expired names

By doing that, it is also a way for these registrars to get the names to be sold for higher prices rather than the basic registration fees, as long as there are interested buyers.

If the name of interest to you is presently taken by these 'sharks', chances are that you will have to approach them and pay a higher price to buy it. As they are provided with a grace period of a few days, in which they can cancel the domains registered without having to pay for it, there is virtually no risk at all for them. With those domains that have traffic, it may even provides them with revenue from clicks generated on their search page at no additional cost.

If you do not wish to buy the domain at a higher premium, you will have to wait for them to drop the name back into the pool in about a week's time.

This is provided the name itself doesn't generate much hits. If it does, it won't be dropped and you'll have no choice but to buy it off them (probably at an even higher premium) or let the name be gone for good.

Following is some interesting points put forth by primacomputer at Namepro.

http://www.namepros.com/showthread.php?t=129538

The names you see grabbed and then dropped a few days later are being used in a scam that allows people to test domain traffic before paying for the domain. Basically they register the name, monitor the traffic for a few days, and then cancel within the "grace period" where they can get a refund. In many cases I don't even think there is any payment and refund. I reckon the registrar is in in the scam.

But like I said people do research into what others are researching. I keep a list of names that are registered and dropped in a short period of time. That way when I see one of these names for sale with high traffic numbers I know it's probably artificial. The pros have already caught the name and thrown it back because it was worthless. So I can just ignore that name as well as future offerings by the same seller.

I've seen a five-day grace period at some registrars. Others don't offer it.

I don't know exactly how they are able to offer this. Some registrars claim they can't offer this service because they are billed the instant a name is registered. Ironically these same registrars hold on to name that have expired and auction them off. So if they are crooks they are probably liars as well.

So if you are counting and waiting for an expired domain name to be deleted, the chances of getting it is virtually zero. Few days after the expiry, if the name is available, it is probably useless, traffic wise. The one that are producing a decent amount of traffic will never be release to the pool again.

Reasons why some expired domains are impossible to register
Why registrars are holding on to the expired names