Tons of links with the same anchor from one forum won't be beneficial like one link from different forums and different anchor text. The second option is natural.
Form is a good platform with respect to SEO. On the other hand forum are good source of information of any topic
Forum linking is important, but it is more important to make sure they are do follow links and use anchor text when linking using you keywords.
You need to enter the right forum associated to your area of interest. You will find a lot of forums on-line in which discussions go about technology, computer systems, business, cars, web mastering, etc. After finding the right forum, you have to read carefully what’s discussed and if you know the answer for the queries people ask, you can give your answers. But you must always give responsible replies. This will increase your reputation as a knowledgeable person. The people who are attracted by your responsible reply may also click the hyperlinks and go to your site. Like this, you are able to get some visitors too. Therefore forums are of great help to those want to develop quick links.
another perspective, if you have used attractive or focused keywords in your forums links, there are good chances of getting your traffic increased( if some one really needs to visit your website ) ...
To me its either high page rank forum or low page rank forum that does not matter.If the forum you are working related with your niche than It is gonna help you from all sides in your SEO effort.
It does matter to your page rank results however and that will drive more traffic to you over time if you can manage to rank you page high on the SEO for your specific keywords. It is easier said than done, for certain high demand keywords, there is a lot of competition that have a lot of knowledge. But personally forum reading is key to understanding and learning real time techniques. To sum it up, they are both important for different reasons.
I'm curious, if I anchor keywords in my signature eg "AAA AAA". After 2 weeks, I changed my keywords to "BBB BBB", will the old keywords "AAA AAA" be still inside my posts?
Anchor Text is a link to your website with a keyword or keyword phrase used to direct the traffic to your site. An example of this is if I link the word Seattle to my city info page so the keyword seattle is associated with the site. Now does a no follow anchor text give any SEO cred though?
I can vouch for the effectiveness of forum posting. Although you still have to try other SEO ways to have a variety of backlinks. If your links are just coming from a single source, then it would no be enough.