I agree with what Kristie said. It's nice to have a resource to supplement the information you get from your vet - or to hear from others how they have managed conditions, such as rehab from ACL surgery, or to share experience with getting insulin regulated and such.
The internet should NEVER replace a relationship with a good vet however.
I use multiple vets - the one by my house is great for vaccinations and general maintenance, but they are not great at hearing zebras instead of horses when quirky issues arise. I have another vet who has a kennel of Setters and Pointers and understands how to do excellent OFA's and "gets it" when it comes to a multiple-dog household. Then there's a great diagnostic guy locally AND the orthopod AND the eye doc............ so far.
Two quick case studies: A friend of mine had a GSD puppy that was limping, joints were swollen and warm to the touch. Took him to the "maintenance" vet I use. The dog was diagnosed with HOD and she was told she would probably have to put the puppy down - X-rays were taken to confirm the diagnosis. She called me in tears - she was feeding a large breed puppy food (24/12), so we didn't think HOD was the cause. I poured over the internet, found a website that mentioned that in Danes and GSDs, sometimes reaction to a vaccine can cause symptoms that mimic HOD. She went to the diagnostic vet armed with the information, and he agreed. The dog is now 8 years old, has a UDX and is halfway to an OTCH, and does Schutzhund work, never having a problem again.
Second: My big goofy guy developed a swollen hock. My maintenance vet will NOT refer to the orthopod (they told me they could do an ACL repair as well as the orthopod could, so I went to another vet for a referral when one guy blew his) since they "don't like him" so they wanted me to go to get an MRI done on the hock - to the tune of $1200. Wouldn't shoot an x-ray, said it wasn't necessary. I went to the diagnostic vet, who shot a $45 x-ray and determined the problem was degenerative arthritis and bursitis. He's retired from field work now but is happy and doing other things with me with the condition totlaly managed with Synovi G3 and an occasional anti-inflammatory on a bad day or preventatively if we're going to the farm.
The danger comes when people think the internet can replace their vet. It can't, but it can help provide additional information.