I know that ideally most of us want various sources of income, ie diversification. But, when it comes to discussing individual sites, I've been seeing two opposing schools of thought.
1. Focus on your one method of monetisation. If it's AdSense then don't create distractions for people by promoting things as an affiliate as well.
2. Diversification makes you stronger, so if there are five ways of monetising your site, then use them (subject to not adding them all at once and overwhelming the place).
I would definitely agree that diversion is desirable for a portfolio of sites, but I'm undecided about it for individual sites. Even then, would the size of the site not influence your decision about focus v diversification? A small highly-targeted site, earning from AS, may well be hampered by having aff offerings on there too. OTOH a really large site might benefit from having a variety of revenue streams.
All the debate I've read so far (maybe not enough!) comes down strongly on one side or the other - but none I've seen so far ever mentioned that different strategies could depend on the size of the site in question. I'm sure that there are other reasons why you might say "it depends", so I thought it might be interesting to discuss them.