I think there must be judgement for each cases. Personally, I make zero--absolutely zero dollars--from my youtube homepage. I've chosen that because I personally hate clicking on the stupid "x" to stop that ad banner. The money that I would make is miniscule.

That being said, if someone has a blog that is supported with an ad banner--just like flyertalk has these ads on the right hand panel & above the area where you're reading--I think that's okay also. If the guy/gal wants to make a few bucks with their blog, I think that's fine, just like the ads support flyertalk. I doubt that there are really any people making a fortune off a travel blog (except for people like Rick Steves, etc).

However, if it is a link to a clearly commercial spam/sales site, then I think that needs to be banned. If someone makes you click a link just for the purpose of selling you something that clearly is a commercial product, that should be deleted.

Thus, I think judgement for each type of external link, unfortunately needs to be made.