First of all, don't want to be rude but I don't want to read your theories or your "I think"s, I want to read actual experiences so I can verify this. Say you find a search phrase at overture, for example, "red amazon apples". You then go your registar and get hold of redamazonapples.com and build a small site. Had anyone done this? Did it help you rank for that keyword without much effort?
No it wont really help. The reason why is because even specific niches such as 'red amazon apples' are dominated by big PY7+ coprs and directories (wikipedia, about.com, answer.com etc) that hog up most terms whihc have commerical aspects to them. You will have to actually come up with brand new non competitive non commercial niche terms. I have built many niche sites using prases around 'work at home' etc and even with the 5 word phrases in the domain I usually only got 3 hits a day (all from Canada) do to this. The serps for my 5 KW domain site were horrible. All it really comes down to are the root keywords you choose and 99 percent of them aren't very good.
The keywords in the domain by themselves arent enough to get you any rankings. If you throw in some on-page SEO, you can get rankings for low competitive keywords.
Well of course I know that, I am just wondering if it will give you an extra boost since you have the exact url of what people are looking for
Noone can tell you for certain how much of a boost the domain name can offer if any at all. But every little bit helps.
It very much depends on the competiveness of the keywords. I have a domain name 'Use SEO' and 'Free Codes' (without hyphen) which I bought around the same time. The SEO site ranked the first without much work. Reason? Nobody searches 'Use SEO'. Therefore, no competition On the other hand, my 'Free Codes' domain never appears in the SERP.. Keywords in domain names will give you a nice little boost but when things get tough, its falling back to your SEO knowledge / experiences.