I recently bought a Tetratec 700 external filter from the shop. It cost me around £20 more than I could have paid online, but I chose to give the shop my money because of the advice, attitude and sheer bloody knowledge I've had from him.
Just to play devils advocate for a bit I think in what you've just said you've hit upon the crux of the problem. I'm not saying its right but the owners of these shops are having a hard time trying to compete with internet business.
Having worked in an lfs for a few years and having seen the change in buying habbits of customers its quite noticeable. Then you get customers coming in and asking for advice about the products they bought online ... but thats another rant for another time
The point I would like to make is simply that with everyone turing to the internet shop keeper's cannot afford to employ the knowledgeable staff that we all would like them to have. I admit that this is no excuse for poor knowledge in staff as anyone worth their salt would have set up a training programme. But when many people, including the person I work for are having a hard enough time making ends meet to stay open month to month (and yes it is a good shop) then sometimes things can slip, but don't just say it on here tell the boss, 99 times out of 100 if no one else cares they do and they'll make sure its sorted and will be happy to have been informed.
Just a thought
Sort of a catch 22 then because I try to avoid pet stores as much as possible due to no staff now days having the knowledge. If I found a good pet shop like vinylman has then i also wouldnt mind paying over the odds and giving that store the money.