Your other option when trying to make money online is “pay-per-action” ads.  

These are typically for retailers, think companies like Amazon and Dell. If you show their ads and someone clicks through and actually buys something you get a commission.

So a lot of people ask:  "How exactly do they know who sent them the link?"    

Typically you would have a website catering to a certain interest group; for example:  Photographers.  It would be impossible for you to approach Sony on your own; but very easy to become an “affiliate” by requesting links from an online broker like LinkShare.

These link brokers establish relationships with different vendors and handle all the link creation, tracking and payment.  For you as the webmaster they create an account for you which produces links hard-coded with an affiliate ID.  Here's an example:

www.yourlinkbroker.com?Affiliate=Sony

In the code you pasted into your site there is another tag identifying the source of the referral (that's you...)  Here's an example:  

www.yourlinkbroker.com?Affiliate=Sony&WebsitePartner=Yoursite

When someone clicks on the link they are sent to the Sony website.  A “cookie” is placed in the browser which then is set as the “referral source”. 

This information would then be retained in the cookie, if someone then buys something from the website that day (or within the 30-60 days typical of these type of agreements…) then this matches the referral ID and you would be credited with a portion of the sale.

Sounds interesting.  But I have never had much luck with these programs, most of the benefit goes to the vendor.  While you serve 500,000 impressions at no cost to them they build their brand. 

If someone set’s their browser to empty or block cookies you will never see the commission.  There are a million problems with these types of schemes and like I said I never had much luck with them.

Perhaps it would be different if I had a forum reviewing cameras, but I doubt it.  People tend to do their research for products online, then buy from the local vendor.  

There is one exception:  Web services:  If you have to download or pay to see it you could see some $$$ from these types of programs.