Same here. I get about $20-30 bucks a month from some random cat videos, and some stupid videos where I strip down some obsolete LAN stuff.
Looking at the ad statistics, about 3/4 of the hits are "non-monetizable", which basically means ad-blocked, iphones or earlier version android devices.
The video uploader can choose the style of ads. Either a small banner at bottom of screen, or pre-roll. I tend not to use the pre-rolls as they annoy me, but they bring in about 5-10x the revenue of banners (unless the videos attract "valuable" ads, e.g. my SFP and Xenpack smash-up videos, bring in up to $5 per click). Somewhat irritatingly, youtube have recently made pre-roll ads the default (it used to be banners only as default), so I have to manually tweak each video after uploading. However, this was done to support android devices, which don't support the banner ads.
I also shoot and edit my videos with the ad banners in mind, so they don't get in the way of anything interesting.
The real nuisance ads, are the non-skippable pre-roll ads. These generally only get used by corporations (e.g. record companies) either for their own stuff, or if they get a copyright match on an uploaded video.