OK, let's say you have a domain name: domain.com and you assign 5 nameservers to this domain name each from different providers / different servers (for example: enom nameservers, zoneedit, your own nameserver on a dedicated box, etc).
When I check domain.com using dnsstuff.com, some of these namservers responds slower than the others (varies from 90 to 250-300 ms) but all of them work. Is it better to keep only the fastest 2 nameservers or is it OK to use all 5? Are there any disadvantages of using all of the nameservers?

Any comment is welcome.

The more nameservers - the better. Look, for example, how many nameservers ups.com has.

Another thing is that when you check your domain using dnsstuff, the answers you get is dnsstuff-specific. You'll get COMPLETELY different results checking your domain from locations in, say, Zimbabwe or SriLanka.

Thanks. In this case, does the order of nameservers matter? Should I always put the most reliable nameservers in front? Or it doesn't matter?

I don't thikn the order matters, I believe (this is my primitive and possibly incorrect understanding) that more nameservers just means it will use the ones with the fastest response time for each person. So if you spread them out globally, people in america get american nameservers responding while people in europe would have the european ones responding to their requests, etc, etc, etc.

Here are my understandings:

The order of inquiries is
1. Cashed nameservers
2. Primary nameserver
3. Secondary nameserver

Most of the time we use the cashed nemeservers, therefore the order of nameservers doesn't a matter. However, when we change the settings of nameservers, the reliability of primary nameserver and the order of nemeservers became a matter. (e.g. Dynamic DNS , Failover DNS)

Originally posted by zoli
Thanks. In this case, does the order of nameservers matter? Should I always put the most reliable nameservers in front? Or it doesn't matter?

The order of the name servers does not matter at all.
The name servers returned from the root name servers (or the glue records of the authoritative name servers) returns a list of name servers in random order.
It works in a round robin effect so all name servers wil be load balanced and hit about the same amount of time.
Using more name servers is "usually" better.
A resolving name server will keep going down the list of name servers until it finds one that has a valid answer or until it times out. So it depends on your resolving name servers if they will all be queried or not.