And don't forget that you don't have to respond at all if you don't want to. In fact, I'd say that most people who 'Like' a post or a photo or whatever, would never expect a response.
Hope that helps.
Katie :)
Apart from loving the attention LOL, it's nice when someone responds, it starts interaction and is appreciated. When someone joins and you ''like it'' at least they know their joining and any effort they have put into making a statement/introduction has been noticed.