What are the benifits of a sitewide backlink to a web page? Is there a negative side to a sitewide link like this?
There are lots of times sitewide links are appropriate - in the footer of websites sharing a parent company, when permanent navigation falls across multiple domains, or in blogrolls, which commonly appear on every page of a blog.
I also read that links between sites you own it will not carry much weight, so doing a site wide link in a triangle will not carry much weight? or is it better left alone and work on other link strategies?
Sitewide links are often not natural, though sitewide blogroll links can still be considered natural links.
Sitewide blogroll links are good for Yahoo. As Yahoo doesn't look at domain only, like Google does. It also increases your visibility, that means you'll get more visitors. Maybe not a lot, but even a little extra free traffic is welcome.
so in general it looks like what everyone is saying is that it would be a waste of time for serps. But if I am only conserned with PR then go ahead and do it.
I would say if it is good for any other search engine except the big G. Google will make a presumption that the backlinks will only count as one. One domain per backlink really.
The biggest advantage of sitewide link is its easy visibility and maximum link juice coz it is from home page.
Keep in mind that a site wide link's value is primarily due to one thing. It's on the FRONT page or DOMAIN landing page. That the page you really want to be on. The other 99 or 999 pages probably don't do as much as the front. On must backlinking only results in inner page backlinks. That's why I love sitewide backlinks.... You also get the front page! I actually just did about 2 hours of work over last night and this morning and got 15 sitewide backlinks from PR 2 to PR 6! I wrote a little about it on my blog.
I think sitewide links drive in good traffic because the site they are on, it is like they are endorsing your site. So if the site you have your link on is trusted by its customers/visitors, there's a good chance they will want to check out things endorsed by that website as well.