Having more sites is definitely a plus... helps to diversify your income streams. However you won't be able to build an authority site if you have to spread your time across so many smaller sites... so there is a trade-off. My strategy is to build up 2-3 big sites... and 4-5 smaller sites... that is more than enough for me... ;-)
actually its not a bad idea... plus if sites gets good pr, u can sell links plus adsense sounds like a good deal