Baloo is right that ultimately, there is no way to prove for 100% sure that a relationship is real. Sometimes there is only one person who knows whether it's real or not because with marriage fraud, there are plenty of spouses who've been duped. There are statistics available regarding passed/refused applications up to approximately April of 2010. They are downloadable in Excel spreadsheet format and various criteria can be looked at using the drop down boxes. Go here and play around.
http://www.data.gc.ca/default.asp?lang=En&n=C517024E&xsl=datacataloguesearchrenderer%2Cresult&searchoffset=1&searchdisplaycount=10&databasematch=wsforms&filtername=formtype&formtype=DD116BB0-BB54-41A5-B210-D245C0139CA9&keywords=immigration&submit=Search
Accra has been historically refusing approximately 35% of spousal sponsorship cases. That's high. The overall average of refusals in 2009 was approx. 18% which is a point or two higher than it was in the previous 2 years. That's more than 10,000 spousal sponsorship cases refused every year. Hong Kong has the highest rate of refusal, hovering at about 52%!
Here are some of the visa offices with refusal rates over the norm of 18%. These averages are approximate and based on 2009 numbers.
Accra 35%
Hong Kong 52%
Kiev 33%
Bogata 22%
Buenos Aires 33%
Kingston, Jamaica 22%
Lima 25%
Mexico City 23%
Port-au-Prince 34%
Port of Spain 45%
However, ALL offices have refused applications so no matter where your application is being processed, you MUST prove your case.