I was an exclusive lurker for the first few years I browsed boards (kept to smaller ones, 4/8chan didn't feel like my jam, only found out about sushi during (and because of) current reincarnation few years ago), think it can be a good thing. You learn alot, and alot of smaller local cultures are more sensitive to someone just throwing around whatever they feel is okay generic chan behaviour, rather than getting a read on the mood and feel first. Being shy and careful can be a positive trait in some contexts.
I'll echo sentiments above, as long as the intent is positive you usually can't go wrong.
Might be good to keep in mind also, the posters that stopped lurking in general have probably made a fool out of themselves at one point or another, it happens. I've gone lurker again sometimes cause I felt too anxious about some mistake or misstep. It's okay to say you fucked up, nobody's perfect.