I don't know the link to it, but there's a quick video clip of Distilled's Tom Critchlow pointing out that "it's not about building links, but building relationships."  I'd have to agree to a significant degree.

I'm not talking about buying relationships, but I'm talking about doing everything you can to get to know everyone and everybody in the SEO community who's good.  Go to all the conferences where they "hang" and spend time going to all the "Link Love", "Search Love" and all the other SEO Love type of fests.

Also, find ways to build up "relationships" with everyone in your niche by either spending time where they spend time and get to know their needs.  Cozy up to bloggers that blog in your vertical.  Send them nice presents.  Remember their birthdays.  Build relationships!

With an unlimited budget, I would seriously spend a lot of it building relationships for your client.

I'd agree with EGOL.  Our goal is always to get more domains.

I would argue that having a domain is like having 1 fan.  Having multiple links from the same domain is like that same fan saying different things about you.  The first complement is usually the best, but after that, you know s/he's a fan and so you listen to the 2nd, 3rd and additional complements less so.

Also, just fyi Pedro, but I think domains is more important of a metric in general from all the work I've done.  Each domain is a unique website and most likely a better vote than 100 links from the same website.  These days there are footer links or sidebar links in a lot of Content Management Systems (cms's) and they replicate multiple links from multiple blog posts or pages on the site.  So, you may seen 1000+ links from one website.  However, in my humble opinion and from what I've seen over many websites, google is counting the domains you're getting links from more than they are all the different links from the individual domains.

For example, let's equate links to fans.  If you had 100 fans, but one of those fans gave you 100 complements, how would an outsider take each of those complements.  I would argue the outsider (i.e., Google) would give credit to the one fan & not necessarily the 99 extra complements.  While it's great to see all the 100 complements from an outsider's perspective, most likely that outsider would give you credit for just the one fan complementing you.  Does that make sense?

I'm not sure if you should worry about interlinking the sites together.  While you might not get extra benefit from them if Google sees that they're all coming from a known network of sites that are interlinked, I would hesitate to believe Google would punish you per se.

For example, Expedia.com has a ton of sites within their company.  So does Amazon.  Do they get punished for interlinking them all?  No.

However, if you're trying to secure extra credit for the links, you might have to get somewhat smart about how you link to each other, but there's plenty of documentation online to explain some of the strategies you can apply to do that.

Interesting data about the hyphenated domains.  Intuitively for me, people just don't type hyphens between words.  So, outside of the SEO aspect of the domains, the "usability" of the domains has something to do with what I'd argue would get more traffic to the domain withOUT the hyphens.  There's some research that says people type in domains "as is" into the url bar the a .com at the end and I'd argue they never put the hyphens in there.

Like the previous 3 comments, in terms of SEO value, they're the same, but Rob's data is fascinating.  If there are manual raters out there checking out the hyphenated versions of domains, there may be a reluctance to value these domains and frankly, almost every hyphenated domain I've ever seen has "less quality" than the non-hyphenated ones.  Definitely can't be proven via data, but just my gut...

I usually go for the plural if I can because it includes the possibility of the singular being hit.   However, there are some terms that the plural and the singular versions have two distinct linguistic intent. Google will eventually get smart about this and has already in some cases, but for products like you're describing above, I usually try to do the plural version if at all possible.