Checking proxy against website question.

I am checking tons of proxies against a website to see which ones I can use.

Is there any downside to this? if I check 1000 proxies and only 50 work that means that the specific website will only see those 50 connections not as some sort of attack or anything.

Please correct me if I'm wrong.

alot of sites have public proxies banned from logins
so its a bit trial and error really