Right, some of you twats obvisouly just looked at the homepage of each site and decided to form your judgement on that. If you're basing your decision on just the homepage, then the similarities are slight.
What you should have done, however, is to perform a search and then look at the results page. Here you'll see the similarities are much more prominent.
As that was obviously too hard for you (supposed IT professionals) to do, I've done it for you and uploaded a screenshot to one of the few imagehosting sites that's not blocked at my place of work...
Now do you see why Kayak are so pissed off? It's not just the same orange-coloured button on a white background any more, is it, you dumb fucks?
ps - Hats off to Kayak for not assuming I'm gonna buy plane tickets in US dollars.... ffs, the whole world does not revolve around the United States of Dumbass America!
pps - can you guess where I want to go on my hols...? ;-)