Every membership counts. Who do you think carries more weight with politicians - an Association with 100,000 members, or one with >2,000,000 voting members? Not to say that you shouldn't join other associations, just don't leave out the NRA.
Remember, politicians are still scared of the NRA. Many elections have been won and lost based on the support or lack of support by the NRA. I think Bill Clinton, Ted Kennedy, Metzenbaum, etc. would be ecstatic with the number of legal gun owners who are not members of the NRA.
Just imagine the bargaining power they would have if half the gun owners joined. We're talking 10% of the US population, and an even higher percentage of voters. Supporting gun control would end your political career, and quickly.
As it stands now, the NRA consists of about 1% of the population (although they represent more) and they're still pretty effective. But they're operating from weakness, not strength. They loose a few hardcore RKBA types when they compromise, but think how many of your "average" gunowners won't join or renew their memberships because they believe that trigger locks should be required, large capacity magazines should be banned, nobody needs an assault rifle or select fire weapon, etc....
It's a lose-lose situation for the NRA - compromise, and some of your biggest supporters bail on you; don't compromise and a larger group of more "mainstream" members will bail on you. The gun control fanatics have been steadily weakening the NRA by pushing the idea that "The NRA doesn't represent YOU - they're too [pick one - radical/compromising]. You're not a
[extremist/liberal] are you?"
