personally i think Poser is a strong word, that really isnt a good one to use. But with that being said, owning a bike DOES NOT make you a biker.
Definitions aside, a biker is one that IMO rides alot, lives the life style to a point(not the outlaw side), and abides by certain unwritten rules, is there for his friends thick and thin, respect for other riders, actually takes the time to stop if he sees a bike on the side of the road and help in any way possible, not just ride by without so much as a glance. and also knows a bit about bike politics(if you have to ask, probably not a biker)
now if you own a bike and get out on the weekends, or from time to time, maybe motorcycle entheusiest is a better word, or maybe even weekend warrior. Dressing in leathers, with HOG patches also doesnt make you a biker. If you wash your bike more than you ride it, probably not a biker. if you ride by a motorcyclest in need withouth stopping, you definitly arnt a biker. if you have the harley boots, harley shirt, harley wallet, harley underwear, socks, bandana, and only wear em on your once a month jount through the country side, again, probably not a biker.(this would be my closest definition of a poser)
As for me, i consider myself a biker and a patch holder, and know first hand what the brotherhood of bikers is. i do everything listed above and I also clock in 20k a year, ride daily, a hard rain the only thing keeping the bike in the garage, although i wear a suit and tie for work, i always have on biker attire underneath(not HD attire), and never take off my rings and ear ring.
sure its mostly an opinion and each of us has a different one, but you can pick a non biker or weekend warrior out of a crowd as well as the hardcore rider.....