How many votes per IP should I allow for a poll?

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1

I’m creating a simple poll module where I pose the user a question and give several possible answers they can choose from.

What I want is to avoid skewing of the results by users that fill in the poll multiple times. Of course the simple solution is to set a cookie that the poll is answered by a user, and check for this cookie. If the cookie is present the user can not vote again.

The problem with this simple approach is that a) some users don’t have cookies enabled and b) users can delete the cookie and be able to vote again.

To this end I would also like to restrict the number of votes per IP. I have however no idea what limit I should set this restriction to.
To be more specific, I want to allow people in a simple SOHO network with NAT to be able to vote multiple times (from different machines).

So I guess the real question is, how big can I expect SOHO networks to be?

2

A single IP address used by a big company for their internet access may have 10,000 different prople all use it and all wanting to vote.

A dynamic IP address allocated by an ISP to different people might have dozens of different people use it during the one day.

A single person using a dynamic IP address may have dozens of different IP addresses when they visit your page to vote during the one day. A little work using proxies and they could still vote hundreds of times a day even if you restricted it to one vote per IP.

3

omg, I forgot about dynamic IP addresses…
Well, I guess I’ll just use a guestimate like 100 or 200 or something.
Maybe also impose a time limit per IP (no more that 1 votes in 5 seconds per IP or sth like that).