Stupid question, I have seen my competitors using a lot of tags for their listings in bookmarking sites. For example: cheap used cars trucks vans I only use two tags used cars assuming all other factors are equal, which one has higher probability to appear first in google and bookmarking site search engine for "used cars"? the one with only 2 tags or the other? Thanks
Using only two tags all the time will likely get you pinged for over-optimisation. It is good practice to use different terms to make it look natural. And to be honest, the impact that a bookmarking site has on Google's index is at most negligible.