The zero budget "This time next year we'll be millionaires" kind of thinking!

Absolutely. It sound too good to be truth.

You should avoid using them because they decrease the value of the domain name. Domain names with hyphen or underscore are less professional.

Originally Posted by MeRulez777

Domain names with hyphen or underscore are less professional.

A: Underscrores CANNOT be used in hostnames


B: Did you happen to notice the hostmame of this forum????

One can use both but hyphens could be more better.

Originally Posted by rkraj2009

One can use both but hyphens could be more better.

http://www.faqs.org/rfcs/rfc1033.html

NAMES

A domain name is a sequence of labels separated by dots.

Domain names in the zone files can be one of two types, either
absolute or relative. An absolute name is the fully qualified domain
name and is terminated with a period. A relative name does not
terminate with a period, and the current default domain is appended
to it. The default domain is usually the name of the domain that was
specified in the boot file that loads each zone.

The domain system allows a label to contain any 8-bit character.
Although the domain system has no restrictions, other protocols such
as SMTP do have name restrictions. Because of other protocol
restrictions, only the following characters are recommended for use
in a host name (besides the dot separator):

"A-Z", "a-z", "0-9", dash and underscore

Yes, the underscore can be used in hostnames BUT SMTP servers do have further restrictions on allowed characters and the underscore is not allowed in SMTP hostnames for some servers