I have recently purchased a pr3 backlink which is related to my blog. I have noticed that there are heaps (368!) of outbound links on the page in which my anchor backlink is on. Does this significantly reduce the link juice which i'm getting?
Yes, it reduces it greatly. Optimally you want your outbound link on a page with as few outbound links as possible. Now you only get 1/368 of that pagerank 3 being passed to your site.
Here are some useful information about outbound links, worth to read; http://googlewebmastercentral.blogspot.com/2008/10/linking-out-often-its-just-applying.html
You will find that if you purchase links, you will not get what you thing you are getting. You will get more links if you use you DP sig links.
Definitely it will reduce link juice. You have to be careful while buying links. Check pages where your link is going to be listed.
I think so, you shouldn't buy the links, the link sellers always sell the links to bounth of other webmasters.
Nothing is illegal until you get caught and the same applies here. To be on the safer side stay away from buying links. When getting links it is advisable that the total number of links on the link page (both internal and external) is less to 75.