The fart apps jokes are getting a tad bit old.
Seriously.
Like QCassidy352 said so well, there are thousands of apps that aren't games and aren't silly to be bought. And even if some apps are silly, so freakin' what? People are allowed a little levity in their lives (and phones) without the delivery system being dismissed as worthless. I have some games and the occasional iPint and LightSaber myself, and I don't feel bad about any of it.
As for the deletion question, I just checked, and I have 138 apps in my iTunes, and probably have about 80 in my iPhone (BTW, that's a much higher retention rate than I had on my Palm devices). Of those, I use probably 20 weekly, but the rest are there in case I need them, like Pet First Aid, or WhitePages Mobile. That doesn't make them less important.
Though I hope I'll never have to use Pet First Aid, I'm very glad to have it.