Your experience may be anecdotal, but it's also supported by data:

1. The 2008 Berkeley Patent Survey (http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1429049), finding that while only 25% of all software startups file patents, about 67% of venture-funded startups do.

2. "Do Patents Facilitate Financing in the Software Industry?", Ronald J. Mann, 2005, (http://papers.ssrn.com/sol3/papers.cfm?abstract_id=510103), finding that the answer seem to be "yes", amongst other interesting conclusions.