Yes, Jim's right that, if you earn at the same rate and the site grows its membership, then your % of the company will gradually decrease. But what's important is the actual value of your shares, not what % of the company you own.
The best way to think about this is, if the shares were actually quoted on a stock exchange, what would be the effect of the site growing on the company's "share price"?
The obvious criticism of the imutual model is that, as we keep issuing more shares, we are diluting existing shareholders. But our policy is to issue shares in a consistent manner and commensurate with the value that a member's actions are adding to the company.
If you agree that we are
doing that, then at worst the issuing of more shares has a neutral effect on the value of your existing shareholding. Because the company's value increases in proportion to the shares being issued
BUT I would go further than that. In the world of corporate acquisitions, company's tend to attract a higher 'multiple' if they are 'big' and 'growing' (excuse the simplistic terms, but I think you get my point). Take the 'big' point first:
An investor wants to purchase a cashback website and has a choice between company A (membership of 100,000) and company B (membership of 1,000,000). Assuming both companies generate similar revenue-per-member, you might assume that company B ought to be worth ten times more than company A. Not so - it will be worth much more than ten times the value of company B, all other things remaining equal. That's because the investor knows that the 1m person membership of company B offers much greater opportunities; go to a retailer and say "what can you offer our 1m members?" and you get a much better response than if you say "what can you offer our 100,000 members?". Also, there is always a 'market leader' premium; investors in companies such as ours generally want to buy 'winners' and then consolidate that position, not buy a company in 2nd or 3rd place and take on the difficult task of overtaking an establish leader. Finally, going through the process of an acquisition is costly and time-consuming, and a company needs to be of a certain size to make the whole exercise worthwhile for the buyer.
The bottom line, size IS (almost) everything.
Investors also like to see that a site is growing. Continuing to attract members via the share offer makes imutual more attractive, because it demonstrates its 'potential' to keep increasing in size and value. I trust I don't need to expand on that point any further
Note that, in the short term, I consider this to be a hypothetical discussion. I imagine we are many years away from attracting such an offer, but even so, it's important to understand that you benefit from growth of the site, even though it reduces your % shareholding.