Food blogs are funny things. Ultimately it is just one person's snapshot view of a restaurant. What would bring you to read my views on a restaurant you may well never visit? I guess like all critics, as a s/he is read more and more, the reader compares it with their own experiences and they learn to trust the critic's opinion, or not. They may also come for the writing, or they may even come to satisfy their raging food-porn obsession if the blogger has spent a suitably grotesque amount of money on the latest SLR wonder box of tricks. Did you SEE the bokeh on those?!
Food critics for the New York Times have rules about the number of times they have to eat at a restaurant before they can review it. As to with the Michelin process. Too many times have I seen negative reviews because the kitchen sent a few bad plates out of the thousands that week. It may even have been the only bad plates to get through the pass all year. Nonetheless, bloggers often write up a scathing review and move on to the next terrified bastard holding everyone to Michelin levels. For things that are cheaper like burgers/street food, I will generally try to go several times before writing it up. I understand that everyone pays the same amount for each plate but if only 1% of the orders are duds then it is unfair to say the quality is poor if you’ve only been once and gotten unlucky.