ur opinions please-internet browsing interferring with online gaming?

im really curious to see what you guys think, maybe you could settle a big argument in my household.
With an internet cable modem connection that is a shared bandwith, how much does this shared bandwith affect internet gaming such as online poker? does opening a browser for normal internet activities(not downloading huge files) while playing online increase your chances of having your game bogged down? With a shared bandwith is it safe to say that in order for my connection to slow down to the point where gaming connections are affected everyone in my neighborhood would have to be online downloading huge files? any opinions are appreciated thanks!