I agree with the general sentiment (don't deface your hobbyist site with ads until you want to seriously monetize it) but I disagree with his solution. He basically advocates "just suck it up -- $100 / month is not that much."

To many people that is a ton of money. A better solution would be to

a) switch to something like Google App Engine which will not charge you a dime until you are serving millions of pages a month.

b) ask a buddy to let you put the site on one of their under utilized servers (this is what I do for my startup, even though we run through terabytes of bandwidth per month)

c) ask a company to sponsor you. Many companies have a plethora of unused servers and would be happy to donate some of that to someone in need.

d) ask the community for donations. I bet you could scrounge up enough to cover hosting, especially if the community realizes that the alternative is ads.

If all of that fails, then go ahead and fallback on adsense - at least you tried.