This is especially important these days because of the rise of mobile phone (smartphones), because I would say about 30-40% of internet users nowadays are doing it on their phones so it's critical to not get left behind when it comes to mobile marketing.
No doubt the kind of marketing we have today, just the effectiveness of video marketing alone is more than enough to sway naysayers towards its direction. I can't even think what more it can do, it's just the perfect way to market a business because it gets the information over quickly without much hassle on the part of the viewer.
Utilize everything that you can for your website's benefit. Blogging, Social Networking sites, link building, forum participation, guestblogging, and a lot more. As long as you're doing all these things consistently and the right way, your website will surely gather tons of traffic with a better ranking in due time.
Of course, PR pretty much means everything when it comes to SEO. It's almost all of the traffic that is coming into our websites. So a better ranking in a good niche means good money. That's all there is to it.
True, I normally use 2-4 primary keywords then a lot of other keywords with different URLs to mix it up a little bit more. SEO is starting to penalize sites focusing on certain keywords for the most part. There's no particular rule regarding this but it's pretty much like that.