Haha, yes I woke this one from the dead. I was searching for an official quote I thought I had seen from Instagram regarding developing (or not) for Windows Phone 8 and stumbled upon this. To answer your question, it is not necessary but if they are going to continue going around filtering 3rd party app users as "spam", which will happen, then an official application will always be superior in regards to uptime.
Originally Posted by iamtim
Instagram is a completely disposable service as far as I can tell at this point (my opinion might change), but I think that almost 15,000 users signing that petition, and that likely being a small fraction of the people that use Instagram's service on Windows Phone and also knew about the petition, proves those users should not be taken for granted. Just make an app already.