The blog happened to be a marketing tool of a company providing some kind of educational services. I contacted the company and requested to remove it. This happened soon but they ended up replacing it with someone else's copyrighted photo. I don't know if permission was asked... I doubt.
There are couple things a photographer can do to protect his assets. Watermarking is quite common but it adds an additional step to the workflow and distracts viewers. Uploading low resolution version only is another way to prevent photos ending up in magazines but it wont stop bloggers.
In case you see your photo used without permission you should contact the admin of the website. Sometimes they react and the photo is removed. In case of printed media like magazines removal is impossible so you should be able to receive some kind of compensation. I am not an expert so I have no clue how much and so on.
But sometimes the website's admin wont do a thing and photo stays online. Depending where the site is hosted a so called 'DMCA takedown' notice could help. I have not tried it myself but I found good information how to write such and to whom to send it.