Notably in this instance, it appears that sharing an app on the Google play web interface to Google+ does not actually share a link to to said app.
To be clear, with any other Google product I would have searched for a contact under layers of help, or shared privately on g+ or posted to the help forums. I am generally a huge fan and sometimes staunch advocate of all things Google, and, though I have had my frustrations, have for the most part aired them quietly and patiently, and been rewarded by what is overwhelmingly the best set of products of its kind. Play, by contrast, seems to be the antithisis of all other things Google at every point, from failing at the start to provide basic access to a full list of programs downloaded (despite the existance of the Chrome store before android market) to a continued inability to delete those programs downloaded once, for free, four years ago, tried twice, then permanantly deleted from my device, from the nearly public online record, or those programs recorded as "downloaded" because a phone with so much bloatware it had to be traded back happened to have that program. Notably, in other media such as books and movies, where people might have whole libraries worth of user data to share with Google, there is no instrument to record any media not purchased through Google.
For a company built on beautiful data organization under a simple and intuitive interface, the base of Play is all flare with disturbingly crippled function. It has, over the years (and I mean years, if you look at the comment boards) become usable (partly by absorbing the books and music teams), but still riddled with embarrassing oversights that would be fine in a beta, but should have long since been ironed out in a division of Google with such a direct profit model.
It would be silly of me to pretend that I won't use play until they fix these issues, and I would even say that, as irritating as they may be, play HAS come a long way, but it has been a frustrating journey, and one that seems to have been much smoother for other parts of Google.