First it must be noted that we can only know if banners are effective if their effect can be measured and plotted against objectives set up for a particular banner campaign.
Banners are being used by B2C and B2B, and in a variety of scenarios. It would be flawed to lump all internet users into one category and dismiss banners altogether.
For example, in the B2B arena, if a decision maker is on a particular site, they may be looking to be sold to. The key is to target the correct sites, the correct locations within those sites, the correct timing, and finally, measure results over time.
Finally, as a B2B marketer, I have found banners effective in conjunction with other marketing techniques and technologies. There are now tools that can connect banners with news relevant to the copy on your banner.