optimum characters for a domain

Is there any research - or is it purely opinion

[canard]

I was wondering if anyone could help - what would you say is the optimum length for a web address? Do you know of any research that has been published on it or is it mostly down to personal preference. Also do you think a company with a long name should go for an abreviation or the full three or four word title?
Any opinions would be appreciated.

[PatrickDeese]

when I pick domain names, I try to avoid using multiple words with repeating adjacent letters:

(these are just things i made up)

wowworld
domainname
novaassociation

I just think they "scan" poorly, and you will lose endless type-in traffic and emails due to errors: novassocation.

I also try not to use really long domain names especially if the word(s) is/are frequently misspelled or easy to mistype.

For instance this would be a bad domain choice (IMHO)

bretttabkewebuyerreferrals.com

most clients would be like "**** is that domain name".

If you go for "branding" make sure that:

1) it is easily pronounceable

2) it doesn't mean something offensive or uncomplimentary in another language.

3) it doesn't rely on "cute spelling": WidgetBest4U.com

4) it doesn't have a common word homonym, in other words, "you" isn't likely to be confused with "ewe" - but IhaveWidgetsToo.com might get a lot of people thinking "Two" or "2".

My rule of thumb is that if you can't tell someone your domain name over the phone without spelling it, you need to pick another domain name.

As far as length, well I might use amazon-books-cds-dvds-clothes-and-more.com to promote a site in the serps, but I definitely would make my contact email address be @amazon.com.

I would guess/hunch is that people are less likely to type in a domain with 20+ letters plus the tld.

Anyhow, shorter is better. You don't think that Amazon launched A9.com instead of AmazonSearch.com "just because" do you?