How important is having a forum on your website? Very important.
Just take a look at Cari.com.my -
Why is having a forum so important?
Getting raw marketing data - almost all online communities have forums. At least that's how people communicate with one another. When people communicate, they use messages and it is from these messages that you can get your marketing information - you can know what people like and what people don't like.
Communicating with your potential customers - let's say you're selling designer jeans and you've built an online community for that designer label. Need to promote your latest line of designer jeans? Do it through the forums!
Selling advertising space - once you've gotten yourself a thriving community - it's time to generate some side income by selling advertising space on your forums.