I'm sure there are instances where scraping websites causes legitimate issues, however most of the complaining I've seen from website operators was the perceived theft of their data. (even though it was publicly available through the browser) Not so much of a bandwidth or performance issue that the scraping causes.

I'm of the opinion that web scraping has an unwarranted bad reputation. As long as I'm respecting your robots.txt and not scraping behind logins, etc... then it's no different than how Google operates.