gentlefoot

They may also think that the second site is masquerading as the first in order to profit from the promotional effort of the first site. Here's an example http://www.twitter.co.uk/
 
Manual penalties are applied in this situation where they come to Google's attention.

site:seemenus.co.uk shows that Google has indexed 13 pages of this site so it is indexed.
 
What keyphrases are you trying to appear on?

So long as the content isn't duplicated then there is some value in doing this if you use domain names that contain targeted keywords. However, any benefit needs to be offset against the extra cost in terms of time and money that numerous sites require. I personally think it is better to focus on promoting one domain name unless your company operates specialist services in multiple niches.