Bans come in strengths. A soft one shows a captcha or an error for a few minutes. A hard one refuses the address for days. Some sites ban a whole subnet when several addresses in it misbehave.
A proxy changes the address, which gets around the ban, but it does not change what caused it. Sending fewer requests per address, keeping the steps of one visit on one address, and sending normal browser headers do more to prevent bans than any number of addresses.
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