I don't consider it a concern for forums in general unless... you are making purchases, using credit cards or bank info
read more about https vs http here.
https://www.instantssl.com/ssl-certificate-products/https.htmlthe nutshell....
Why Is an SSL Certificate Required?
All communications sent over regular HTTP connections are in 'plain text' and can be read by any hacker that manages to break into the connection between your browser and the website. This presents a clear danger if the 'communication' is on an order form and includes your credit card details or social security number. With a HTTPS connection, all communications are securely encrypted. This means that even if somebody managed to break into the connection, they would not be able decrypt any of the data which passes between you and the website.
Benefits of Hypertext Transfer Protocol Secure
The major benefits of a HTTPS certificate are:
Customer information, like credit card numbers, is encrypted and cannot be intercepted
Visitors can verify you are a registered business and that you own the domain
Customers are more likely to trust and complete purchases from sites that use HTTPS