Event posters are an important way for student organizations to get their name out. Unfortunately, the Queer Student Union and its sibling organizations have an almost constant battle to keep up fliers. QSU spends far more money than it should on posters just because of the need to frequently reflier those that are removed.
While I understand that it is easy for organizations to accidently cover up others fliers, there have been cases in the past when certain organizations were targeted. One of these stories was compiled by a Jen McCreight, who noticed that the Queer Student Union, Society of Non-Theist, and Delta Pi Rho fliers were being placed in certain configurations. You can read more of that on her blog at http://www.blaghag.com/2009/08/more-school-drama-flyers.html
The QSU president before me, Jessica Lee, often told a story of a flier she had seen that had been through quite a bit. After it had been posted, the flier was removed, torn in half, and left on the ground. This story luckily has a somewhat hopeful ending, with somebody picking up the two halves of the flier, taping them together, and reposting it.
Whenever QSU has complained about the difficulty of keeping our fliers posted, we have been told nothing can be done unless we catch somebody. This is especially frustrating when entire buildings are sometimes stripped of our fliers. It can also be quite clear when our fliers are selectively removed. We often joined forces to flier with Delta Lambda Phi, Gamma Rho Lambda, Ally Association, and NOGLSTP. It was quite clear when the QSU and NOGLSTP fliers (that boldly have an LGBTQ message) are missing while the DLP and GRL fliers remain (which often have a much more hidden reference to sexual orientation and gender identity in the fine print). Once, NOGLSTP even caught a janitor removing Queer Student Union, NOGLSTP, and Society of Non-Theist fliers claiming they contained objectionable material (merely because they included Gay messages and Atheist messages respectively). NOGLSTP did report this incident.
The removal of fliers has required the LGBTQ organizations (and Society of Non-Theists!) to devote extra time and money to advertisement. I hope one day these advertisements will not be so quickly removed, and that QSU can devote some of that wasted time and money to the events themselves.