At the risk of sounding like (even more of a) stick-in-the-mud regarding the value of vouchers, here is a great example of not always being able to trust photographic identifications of insects:
Scientific American blog of Alex Wild in a post on misidentified insects in the media. Alex has his own excellent blog, Myrmecos, where he has shown that even National Geographic isn't immune to these mistakes (nor The Learning Channel, a Discovery company). Surely they should know better. And so should the "experts" at pest eradication companies around the country, but look at the array of things that are not fire ants displayed on their web sites.
Unfortunately, mislabeled photos online often come back to haunt us, as the misidentifications may be passed on and perpetuated. I'm not going to beat a dead horse here. I'll just say be careful when using photos to ID insects, don't just label something online if you aren't sure (ask for help!), and correct your mistakes in a timely manner.
[stands down from soapbox]