Heh, I'm in college and I still know several people who act exactly like Ron and Lavender. That's why my friends and I created the Sexual Probation Police to keep public decency.

Being serious, though, the romances shown between Harry/Cho, Ginny/all her mans, Ron/Lavender, Hermione/McClaggen Hermione/Ron etc were definitly needed to give the characters an adolescent side and to keep the book not just about gloom and plotting - and to show young teen readers how overly melodramatic they are ^^. I personally found the teenage romantic bickering tiring, but I wouldn't actually want those story lines to be removed from the book.