Official comment
Hi - again, sorry for the length of time it's taken to respond to your question!
I'm afraid there isn't an easy answer to this one...
We undertook a lot of research over the past 12 months looking at how people use the site. The overwhelming feedback on "Back Blips" was that they are hugely confusing. Very few users knew what they were (many asked why some of their entries didn't count toward the number of Blips they had!). We decided that we had to try and solve this problem. This involved combining the entries.
A small number of users have, unfortunately (like xb below) have been affected by this move, meaning that a few people will not have been able to celebrate their Blipfoto anniversary. We are hugely sorry for this. We will do our utmost to make it up to you.
The importance of the 'birthdays' and 'anniversaries' are no less important to us. In fact, we hope that we will be able to reinforce these great little moments that bring the community together even more!