This is a very important question that, unfortunately, many internet marketers seem to pay little or no attention to. The general approach adopted by many internet marketers seems to be that that quantity counts over quality - but is this really the case?
The resounding answer to both these questions is - ABSOLUTELY NOT!.
We need to be very clear that all links are not equal - in fact it is possible to go even further than this and actually say that some links are less than worthless, in fact they may even actually be harmful to your ranking.
If you were to create a ranking list of possible links then this would be the order:-
1) Links from.edu and.gov domains are the "best" types of links a site can get - particularly if the site has a high pagerank as well.
2) Links from well established, high pagerank general domains (e.g..com,.net,.co.uk etc)
3) Links from more recent, lower pagerank sites (i.e. more recently created / less well established sites)
4) General sites
Many of the "Dominate Google" tools and sites that you see that offer an apparent shortcut to getting a top ranking on Google will simply create hundreds of backlinks to your site from their existing network of sites (usually blogs). Whilst this may give a short term boost to your rankings this will not be sustainable. The quality of these links is normally very poor and you will eventually be penalised for these links and your ranking will drop accordingly.
So all links are definitely not the same and you need to invest time and effort in gathering the right type and quality of backlink for your site.