1. Is there anything wrong with having multiple domain names pointing to a single site. Domain names like:
Keyword1Keyword2.com, Keyword2Keword3.com, etc.
2. Is there any benefit to the above, specifically any ranking benefit?
For example, if someone was searched for "Keyword1 Keyword2" would the Keyword1Keyword2.com URL be paired up with my page content to result in a high rank. Likewise, if they searched for "Keyword2 Keyword3" the page content would be paried with keyword2Keyword3.com. Or is it the case that only one URL would ever be used and the others would be ignored by the search engines? If this is the case, then the only use for the other URLs is for the cases when traffic comes from directly typing in the URL.
3. Is there no longer a SE benefit to hyphenating the domain name? Keyword1-Keyword2.com versus Keyword1Keyword2.com
2) There are no ranking benefits to pointing multiple domain names.
3) It is still debatable whether or not there was ever a benefit to hyphenated domains. My experience is that the anchor text will have more impact with how the domain is parsed out, not by hyphen alone. (ex. if the two words in the anchor text are broken apart, then the engines will interpret the domain this way). All said, keywords in the primary domain can definitely have an impact on rankings (hyphenated or not), mainly because it influences keyword based anchor text.
Sites like DMOZ and Google etc I believe will track people trying to get multiple domain names pointing to THE SAME BASIC site, as this just clutters up the directories and indexing.....
No practical experience of it but that's what I read last night on the net.
Cheers
Andrew