Ever since I joined LinkedIn, I've been receiving emails from Google recruiters. I replied to the first one saying that as I'm an established contractor with my own company its difficult to switch to permanent employment. The emails kept coming in on a monthly basis. After around a year, I was on the look out for something different so I decided to look into it. The job description looked interesting and matched the work I'd been involved with in the previous years.
I had the initial pre-screening which had some technical questions and we discussed the role a little.
A week later I was offered a technical phone interview. It started with one question, which kept getting expanded until it covered a wide range of topics. It was clear they were after someone who knew how to approach a new problem, rather than someone who had memorized a bunch of commands suitable only for a particular situation. I felt it went really well, except at the end when I made some silly mistakes, but it was 10pm on a Friday, so I'm sure most people wouldn't be completely switched on at that point. Over all the interview was positive - it was relevant to my skills and the questions were fair.
A few more days passed and I got an email saying that they don't have any jobs which match my qualifications, with the usual "thank you for your interest in our company etc.." Not knowing what that really means, I wrote back asking for a reason, and feedback on the technical interview. I explained where I thought I went wrong, and asked if that was the issue. I only got another email thanking me for my interest in the company and to try again in a few months.
As I only had the technical interview, I was expending something like... "we need someone with more experience/knowledge in xxx", or "someone who has used xxx for xxx years". I did get the impression from the emails that there actually was no job available which was waiting to be filled, but they are constantly on the lookout - in the same was that job agencies sometimes post bogus jobs on job boards to get candidate information, and find out where gaps are in the job market.
I fail to see how applying again in a few months will change things as I'm not sure what went wrong, so will probably make the same mistake again, unless asked exactly the same questions.