Leosghost - 11:32 pm on Mar 7, 2013 (gmt 0)
I think you'll find that how many IBAs you get depends on available ad inventory at any one precise time ( belly fat ads et al are "filler" when nothing else is outbidding them )..and also how specific/precise your site content is ( if it is very specific/precise it will tend to get a higher proportion of site content based ads ..but again, only if they are bidding higher than the others at that time..
Bear in mind also that lawyers in the LA area will have probably not wished to have their ads appear to me in France ..or Billy Joe in Kentucky..( so they won't ) so unless your visitor is from LA, something else has to take their place, even if your site is about LA lawyers..and so on ) ..some sites get a lot more IBAs than others, especially if their content is unfocused , and sometimes the ads are entirely Geo targeted..
Which is why I usually see at least two "expat investment", per page, ads on the BBC..it is a UK based site, and my browser prefs are English, but my IP shows me to be in France ..so G figures ( rightly ) that I'm probably "ex-pat"..and "ex-pat" investment ads pay very well for the publisher..as do all financial service lead ads..
Tangential..I visited ( and ordered from ) Vistaprint directly without passing through "G search"..it was as a result of seeing an offer on French TV..
But their ads are still following me..
So how would G know that I was "interested" ? ( rhetorical question ;)
I have a fixed IP..
Vistaprint runs Ganalytics..
So G knows what I looked at ..how many pages, how long, what sequence, and that I went through the checkout..
So..unless G can read 3rd party cookies..
They are IBAing [sic?] me ..or to be more exact "re-targeting" me based on what they learned from their end of Ganalytics..and the cookies that they are dropping me with it..
Now.. in the above case the site I visited/purchased from gains by G following me with their ads using info from Ganalytics..and G's own cookies..
But if I visit your "informational site"..say it is about DIY ( and you run Ganalytics ) and then I visit another "informational site"..say it too, is about DIY..( and it too runs Ganalytics ) and then I go on to visit a 3rd "informational site"..say it too, is about DIY ..( and it too runs Ganalytics )..( see where I'm going ;)..G now has a pretty good idea that I'm interested in DIY..
So the next site I visit ( or some of the sites I visit over the next 24 hrs , 30 days, year or even more* etc ) will be showing me DIY ads..even if they are about "rock climbing", "car sales" or "medical" sites..
* I still get IBAs shown me on other peoples sites based upon searches and site visits ( and on which I made no purchases ) that I did over 4 years ago..less often than those related to more recent surfing..but they do still try to see if they can rekindle an interest..
Now ..remember all of G's other ad delivery platforms, "double-click" etc, drop cookies on you/me ..which G reads ..and decides which ads to send you/me..whichever adsense site we are on at the time..
Like netmeg said..IBAs are not going to go away..and as jpch also said, G are not the only ones using them..but they do have a major advantage and data gathering reach via Ganalytics over the other ad networks..it is free to you..but it is very very much more beneficial to them..which is why they "give it away"..for now..
IBAs are now a fact of life..and they are definitely good for G's bottom line..if your site is tightly focused on a specific subject, they may not be so good for yours..if it is less focused or "thinner"..you may well do OK or well from them ( ehow is a good example of who makes money via IBAs)..and you don't have to spend a great deal of time to make sites of a high quality about subjects that you know about..you can go the ehow route..as many do..or scrape..as many do..or be ultra thin and unfocused..as many are..
read "source code" of pages that you visit, you'll be amazed / horrified at just how the vast majority of sites worldwide now run Ganalytics, all reporting back to G, then add in all those that run adsense and or doubleclick etc, again all reporting back to G about what everyone who visits does, looks at and how long etc..Oh yeah..and the G+ buttons ..like on WebmasterWorld..which report your IP direct to G for every page that you load which has them..and each time you post they reload, direct from G, with your IP..so they know if they want to crunch the numbers ( and they can "crunch numbers" )..who posted what..and from what IP, and what else you look at anywhere, any site, any search, any time, all of it ;) and if you run adsense, who you are..