What audience thought that she didn't recognise him? It's clear Lois recognises him as the same Clark Kent she was hanging around with for most of the movie. Memory erasing kisses are from another Superman movie series.
The thing I liked most about this film was that it completely did away with the "Lois doesn't know Clark is Superman" story. Instead, she gets to demonstrate that she is a talented experienced journalist and tracks down the mysterious super man to his parent's house. Sure, Clark eventually gets to set up the mild mannered reporter gig, but Lois is better served by never having to go through the "blinded by love" thing (even though I also liked that explanation from Lois and Clark). I've never seen Smallville so I'm not sure how they handled it all, so I thought the movie's take was great.