How many back links would you say are necessary to trigger a Google penalty. I'm not into article writing but will posting on different forums with links in a signature be enough to do so? Or does Google just penalise you if it suspects you of buying links?
The Google slap applies only to Google AdWords. And it depends on what you think excessive SEO is. SEO is never too much... you just need to keep working on it gradually over time and not do a one time bursting SEO campaign and hope it's all said and done for as long as that site is online. Secret to Success there is to go on building 10 - 15 backlinks per month on Related webpages, there is no need to do more than that.
yes too much linking TOO FAST can hurt your site. I spread my linking out over a period of a couple of months, IE: Spend one week building links for X site, swith the next link to building links for XX site, and so on