My Opinion
I looked at the tiered sponsorship plan and, as a person operating his own business I thought I would comment based upon my first reactions to same.
The first thing that I observed was that all of the plans include an option that would require the sponsor to offer club members a 10% discount. Limiting this to dry goods only, from what I have learned the average discount available to a LFS is about 10 - 25% off the manufacturers suggested list price, and that is before shipping expenses etc are added in, with about 15% being more or less typical day-to-day.
So while this is good for members, it is obviously NOT very profitable to the sponsor, especially when shipping, support and returns are taken into consideration.
As an observation, you've probably noticed that some LFS jack their prices beyond the suggested list price, sometimes way beyond, that is in part due to the low (wholesale) margins they operate on and sometimes just out of greed.
The second option, requires that the sponsor pony up a fairly significant contribution, with or without the first option. As a provider of web hosting services, with nearly eight years "in the biz", I can tell you up front that even the tier 1 plan costs more than many (small) businesses spend annually on web hosting and email services.
What needs to be kept in mind is that regardless of the option, the sponsor needs to make a profit, if he can't make one sponsoring BRS, then they are not going to make the effort to the detriment of the BRS members and coffers.
So .. why not look at what your asking and at what your offering the sponsor.
Perhaps they don't need a "forum" but rather just an area into which they can post their weekly or monthly specials. Make it simple for you and them AND cost effective for both parties.
Personally, I dislike banner ads and as a businessman I don't use them, and I wouldn't bother offering them.
Their are a number of other "features" to these sponsorship plans that may or may not be viable, cost effective, manageable etc. that might need to be reviewed, modified or terminated as seen fit.
Anyway, just my observations and food for thought.
Regards
Noel