I was born in Macau and I have a Canadian passport. Do I need to get a visa to go to Guangzhou?

Yes, you need to apply one according to your purpose of coming to Guangzhou.

According to a post from the Canadian government web site (see below) this is no longer required. I wanted to get an official statement from the Chinese government to state that this is true as I will be making a short trip from HK to Guangzhou in October.
http://travel.gc.ca/destinations/china

Canadians born in Hong Kong, Macao or Taiwan
The Chinese government has modified requirements for the issuance of visas to Canadian citizens born in Hong Kong, Macao or Taiwan. Visas will no longer be issued to Canadian passport holders whose place of birth is inscribed as Hong Kong HKG, Macao MAC, or (city name) TWN . Canadian passports issued to Canadians born in Hong Kong, Macao or Taiwan are now issued only with the place of birth and not the three-letter country code.

I think you'd better confirm this with Chinese embassy in your country. I didn't know about what you posted above.

This was a post from the Canadian Government. There is no reason to think that they would publish false information and create havoc for their citizens. This information was posted on the Canadian Government web site indicated in my response to you. I was hoping that there would be a response from the Chinese government but I did not get it. So, I have written to their Consulate in Vancouver asking them to clarify and confirm that visas are not required of Canadian citizens who were born in HK, Macau or Taiwan. I am waiting for their response.

I was asking similar question earlier. Have read your quoted para in email passed along online too. After some research, I think this para is only a statement posted by Canadian Govt to explain a story behind it: in 2003 Chinese govt would not issued it to Canadian passport holders born in Hong Kong, Macao or Taiwan with birthplace shown the country code HKG, MAC or TWN (they wanted "China" instead of these 3 letter code). I assumed Canadian govt did not follow the same, instead, the newer passport issued after July 2003 would show just Hong Kong, Macao or Taiwan (no more country code to avoid the conflict). Therefore this para only means it would not be issued to these 3 letter country code, and it does not mean it is not required for these passport holders. I assume the original sender of that email had misinterrepted the actual meaning of the posted para and I hope it won't turn into a rumor. Under new changes, if you join a less than 5 days tour in Hong Kong and visit cities in the Pearl River Delta (I think it includes Guangzhou), then you don't need one.

I just read your other response from thread no.4. Looks like you've knew all about the latest excemptions already and we both are trying to verify that untrue email rumor.