I wouldn't call Spark Ventures "a black hole" - Skinny does quite well, as does Bigpipe.
Although these two business are not actually part of Spark Ventures. They fall under the HMB division of Spark and their results are fairly reported in Spark's financials.
Spark Ventures remains a black box - ie it's results are reported as 'not material to Spark' meaning they don't disclose the financials. Given what Ventures is supposed to do this is not surprising. Though as a shareholder I'd like to know personally. Lightbox specifically is a black hole - subscriber numbers are not reported, we only know vague estimations of costs ($20-30m etc etc), revenue is not reported.
Edit: To be clear - I didn't mean to imply Spark Ventures was a black hole in terms of sucking money. It is a black box in that its financials are completely opaque. I don't believe Ventures as a whole simply sucks money into the abyss. I realise this was not well worded in my original post.