There is a lot of resources here and on the web explaining how to avoid biaised statistics coming from referals such as Darobar, semalt, iloveitaly, etc. and how to block these malicious bots.
My question is not about how to prevent it to happen. I don't understand WHY i'm getting spammed. What is the interrest of these companies / entities to flood my stats ? They must have a pretty big infrastructure (either servers or infected slave computers) to visit so much websites and so many times. But what is the purpose of all of this ? Is it financial ? malicious ? Just for fun ?
What are the risk for myself or my company ? Can I be disqualified by Adsense or another online advertising program ?
Those bots don't generate ad traffic, even if they do, google and ad companies detect them, I used to work in adserving. Again google, yahoo and major ad serving systems take precautions to prevent fake traffic etc.
Those bots basically searches for things like email adresses, contact information in short any kind of information. Dont forget google uses bots to crawl internet which they have google search engine.
Some bots place comments on higher ranking sites for SEO work.
This is just a big business.
if you want to avoid them, take a loot at here : http://www.robotstxt.org/faq/prevent.html
However, these are just standarts and some folks dont care about them. But then i wouldnt really worry that much.