Any career move needs careful planning.
It is important to be clear about the reasons for making a major career move and to ensure it is part of an overall career plan - or, at least, that it can be explained as such. Almost all IT professionals make regular career moves these days, but a CV with too many fits and starts is not going to look impressive. There are big differences between programmers and business analysts, for instance, and those with good technical skills should think hard before getting into areas such as project management, unless they are sure that is a real career goal for them. On the other hand, future employers will be looking for examples of initiative, which makes this a good time to get into new areas. There may be the chance to rise up the ranks rapidly, due to the greater flexibility and flatter hierarchies in most start-ups, but the entrepreneurial atmosphere also includes long hours and substantial risk.