Personally I would say that if you know you are not doing anything wrong, i.e. you are naturally acquiring links at a steady pace, then you probably don't have anything to worry about regarding the amount, but if you aren't really playing by the rules, i.e. you have some kind of system set up to build you a load of links and you want to know a good number to set it to, then that's pretty much cheating and while I'm not gonna bitch at you for doing it, Google most certainly will if they detect it, and so if you have a system like this or any kind of automatic link building process, then my suggestion would be to keep the numbers low to avoid detection, probably somewhere between 10 and 50 a day would be alright, although 50 a day might be pushing it a bit. Anyway, it seems I've rambled, so to summarise, ask yourself "is my link building method likely to be seen as natural growth by the search engines?" if so then you shouldn't really be able to create enough links in a short enough timeframe to hack Google off, then ask yourself, "or if I really think about it, am I kind of cheating?" if so then I would recommend (if you insist on using the automated system or whatever it may be) keeping the links to a minimum to the point where you're drip-feeding them, but to be honest, you will probably get discovered and thrown out soon enough anyway. If I HAD to take a stab at an ideal number of links for a new site, I'd probably say between 150 and 200 per month, but it's the quality of them you want to really be focusing on. I know nobody really wants to hear this, but the best way to get a site to the top is slow and steady link building (of high quality links of course) and lots of patience.
I guess I should start shaking in my boots once I launch my SEO "Starter" Guide Web site, eh? (Imagine - one Web site, with ALL my SEO knowledge, free for everybody.) Actually, that sums up what I've been saying quite nicely.