Selling on craigslist is a pain in the neck. It usually ends up working out fine for me, but it can be an exercise in frustration. If you list the bike again in the spring, you should be fine. Getting rid of bikes or kayaks in the winter can be difficult. Generally if you post in your ad "price is firm" or something to that extent the lowballers will leave you alone. They might still try...

I usually build in like $20-50 into the price of whatever I'm selling for people that want to bargain. If it makes them feel better that they got $20 or $50 off, that's fine.

but i usually end up relisting things several times before i get a serious buyer... if someone seems like a scam, i usually just do the, this is my phone #, call me if you want to come by - nigerian scammers are not goign to call you or show up to meet you. I did once sell a guy in chicago a kayak that he saw me advertising on the local craigslist - he paypaled me, I verified I had the money, and then I shipped the kayak to him. we split the shipping (which was like $260) . he hadn't been able to find that kayak at a discount anywhere locally. so just because someone is contacting you that wans you to ship, it doesn't mean they're a scam - but I had him call me, and I spent a fair amount of time talking kayaks with him to make sure he was a real person

Several times people will say they're goilng to show up and then just not show up - unless they call me, I won't wait more than 30 mins.