Additional domains for SEO?
I have come across a number of people who register a domain containing the name of their business, then register a string of additional domains with their keywords and re-direct these to their site in the belief that this will improve their ranking in searches for these keywords. e.g. Somebody registers their business as frodosmotors.com and also registers shirecarhire.com, middleearthcarhire.com, car-hire-in-middle-earth.com, etc., re-directing all these to frodosmotors.com.
I have seen no evidence that this technique works, and frankly can't see why it would, but I've been wrong before. :) Can anyone give me genuine information on this point, rather than hearsay and rumour?