Personally, I'd prefer to have 10 visitors a week and convert 9 of them to members, paying customers or clients, but when you multiply that up to equate to the worldwide web, the numbers are unimaginable.
In most of my previous research, conversion rates online are running fairly parallel to every other traditional form of media advertising - 1% can be acceptable, 5% is fairly good and converting more than 10% on a busy can be phenomenal. I trained with a company who classed their salesteam members as failures if we didn't surpass 50% conversion! (Slave drivers!) So it CAN be done - you just need really, really well qualified leads in order to reach those levels. The easy answer is there's no easy answer barring throwing £millions into advertising and settling for a miniscule conversion rate.
Example: look at the likes of eBay against the likes of eBid online auctions. Millions flock to eBay, everyone's heard of it, the web is littered with affiliate links, banner ads, pop-ups, PPC etc, it's on TV, radio, films, sponsorships... they are throwing the name in our faces at every opportunity. The name has become synonymous with online auctions! But look in their forums! They are filled with complaints about their fees, services and alleged atrocious treatment of their sellers. eBid has plenty of fee free options for sellers, but do the grumblers descend en masse to make the most of some money saving and free advertising? No! Why not? Because the site owners don't appear to have a multi-million pound advertising and marketing budget in place that can convince the public that they are worthy.
Think how often you walk past shop windows without going inside. You will still look in the window but unless you are captivated by what you see and get that sudden 'must have' urge, there's nobody at the door to encourage you to enter and shop. That's where blogs and forums come into play - target your specific market and then invite them in... strike up a good rapport with your forum and blog readers and their respect will be repaid many times over by personal recommendations. Get it wrong, however, and you're as well shutting up shop.
Just my personal take on things but I don't really sell products online, so I could be talking absolute nonsense.