Also, if the site has multi-topics, does this mean that it will appear
in many more places with the search engines than it would if it only
had a single topic ?
The more content your site contains, the more chance there is that you will end up ranked for a wider variety of search terms. But the problem is, not really getting ranked, but getting ranked highly for targeted search terms...
In other words, attracting people who will do what you want them to do when they arrive at your site.
One thing I do, is to try and identify less competitive terms that are related to very competitive (and expensive) phrases. I include content to cover both in the site, but rely on on-site links to draw people from SE landing pages to more desirable action pages which never really get much traffic themselves.
This strategy applies to PPC as well as "free" SEs.
The trick is to work out how people think, when it comes to identifying related keywords. It's the mental process that is the crux, not how similar the terms look "on paper".
As regards your general question...
Single topic, or multi-topic websites - which is easier to promote
via the search engines ?
Thus far, the SEs have generally judged sites on a page level. That said, Ken Evoy (Sitesell.com) has been saying that SEs are likely to take more interest in the overall theme of a site (when ranking a page) as time goes on.
I don't know where he gets it from, but I wouldn't bet against it. :wink:
If this does indeed prove to be the trend, the tightly-focused themed site will be the way to go.
Besides, don't make the mistake of trying to be everything to all people. Trying to create a web site that will appeal to everybody is much like the old marketing trap of coming up with a product that "everyone" will want...
But next to nobody will end up buying.
I see marketing as leading people through a maze. Everytime they get to a junction, ask them which way they want to go, and then take them there.
If you make the maze too big, firstly, you'll have more trouble predicting the questions they want answering, and, secondly, you risk getting lost yourself.
Hope this helps,