What are the disadvantages of opening the source of your own science tools
Some disadvantages could be:


People may expect you to maintain the code. If you don't maintain it, the code may be rendered useless at some point.
You might feel forced to document the code. This is actually an advantage, but many people would not realise that ;)
You might have to work on cleaning up the code. Exactly the same point as above applies, if you ever want to re-use your code this is actually an advantage.
If people start using your code (this is not impossible), they could e-mail you and start asking questions. This takes your time. On the other hand, it also provides you the opportunity to be co-author (so hey! don't document, so people are forced to ask your help ;-)


More points are raised in the very similar question that was asked at Programmers.SE less than a month ago:

Why don't research papers that mention custom software release the source code?