Once upon a time this method was pretty good, but these days not so much. For instance spamming hash tags on twitter used to work good, but now Twitter will 'ghost' (like on CL, more on that in a minute) the tweet on the hashtag page when the same link is in it. It is possible to get several domains to try to prevent twitter from seeing it, but I think they have a way to follow the 301 redirect because they will still ghost the tweet.
For Craigslist, you have to post your ads in the W4M sections to promote a dating site. Posting on the W4M section with promotional links is a mother f*cker, next to impossible because when you make the post CL will check the link and if it goes to any kind of promotional link the post will be stopped and they will tell that's the reason why. Using domains with the 301 redirect can still work and the post may be allowed, but there is a really really high chance that the ad will be 'ghosted', in other words won't appear in the W4M section.
Let's say the ad does make it and shows up in the W4M section and now guys will be able to see it, once they see it really isn't a girl looking to hook up they flag the post and it's gone.
I used to use these methods when they worked, not to say they still don't, but the time and effort is just too much now.