What you're saying was the original idea behind meta keywords. The problem is people abused them and stuffed keywords in them until they were impossible to trust. Porn sites used to add the word Disney for example.
In an ideal world if everyone only used meta keywords to honestly describe what a page was about it might have worked, but people didn't always honestly describe what their page was about.
Here's a
good post about the meta keyword tag which will give you some history about the tag and their current usefulness or lack of usefulness. You can see in the post that neither Google nor MSN pay any attention and while Yahoo and Ask both did make use of the tag neither places much importance on it.
At best if you're phrases has little to no competition they could help, but using the phrase once or twice in your page copy or your page title is going to far outweigh their use in the meta keywords tag.
One way you might benefit with the meta keyword tag is to use common misspellings. For example with "MySpace Layouts" lets say you discovered that a good number of people misspelled the word 'layouts' as 'layots' For some reason pretend a lot of people forget to type the 'u' In that case you might want to use 'myspace layot' in your meta keyword tag since you wouldn't want to misspell it on your page. It probably wouldn't have much competition so maybe having it as a meta keyword helps a little.
Search engines have to look to other parts of the page to better decide what a page is about. They do place a lot of emphasis on your page title. Your title is probably the most important words you'll write on your page from the perspective of a search engine. It's pretty important for people too.
Today search engines tend to place more emphasis on what's said about you off your site than they do with what you say about yourself on your site. You still want to optimize your page, but search engines place much more emphasis on link data now. That could always change in the future, but that's the current situation.
When I write a page I will try to get one or two phrases into the page title. I still want to make the page read well to real people.
I'm having trouble accessing the site in your sig right now, but I'm guessing you offer free myspace layouts. You might use a title on your home page like
Free MySpace Codes and Layouts
Short and simple. Other pages might be more specific and you might add calls to action to the title.
I'll also add keyword phrases to page headings where appropriate and generally use them throughout the page. I don't try to stuff them in there though, I just use the words where it makes sense to use them in the copy. Most of the time if you write a page about something you're naturally going to use the words. Writing naturally also has the advantage of picking up search traffic for a wider variety of phrases than you might have intended.
Search engines likely place a little extra emphasis on words that appear inside semantic html like <strong> and <em>. You never want to overdo it though. Always write your copy for the people who are going to read it.
